Allow re-admitting an archived tenant via a brand-new contract

Adds "Wieder aufnehmen" to each archived contract card: landlord picks
a vacant room, move-in date, rent and deposit, then POST
/contracts/reactivate creates a fresh Contract row for that user (new
id, new terms, no carried-over documents/signature) and re-assigns the
room. The old contract is never touched — it stays exactly as-is in
the archive as a historical record, per the requirement that the
original tenancy documentation must be preserved even after rejoining.

New GET /contracts/vacant-rooms lists rooms with no active contract,
used to populate the room picker and prefill sensible rent/deposit
defaults from the room's base rent.

backend/src/routes/contracts.ts

@@ -325,3 +325,73 @@ contractsRouter.get('/contracts/archive', requireAuth, requireRole('LANDLORD', '
   });
   res.status(200).json({ contracts });
 });
+
+// ----------------------------------------------------------------------------
+// ARCHIVIERTEN MIETER WIEDER AUFNEHMEN (neuer Vertrag, alter bleibt im Archiv)
+// ----------------------------------------------------------------------------
+
+// Zimmer ohne aktiven Vertrag — für die Auswahl beim Wiederaufnehmen.
+contractsRouter.get('/contracts/vacant-rooms', requireAuth, requireRole('LANDLORD', 'ADMIN'), async (_req: AuthedRequest, res: Response) => {
+  const rooms = await prisma.room.findMany({
+    where: { contracts: { none: { isActive: true } } },
+    select: { id: true, roomNumber: true, sizeSqm: true, baseRent: true, utilityPauschal: true },
+    orderBy: { roomNumber: 'asc' },
+  });
+  res.status(200).json({ rooms });
+});
+
+// Vermieter/Admin: ein Mieter aus dem Archiv (Contract.isActive=false, User
+// ohne roomId) bekommt einen VÖLLIG NEUEN Vertrag — der alte Vertrag bleibt
+// unverändert als Dokumentation im Archiv stehen, es wird kein alter Vertrag
+// reaktiviert oder überschrieben.
+contractsRouter.post(
+  '/contracts/reactivate',
+  requireAuth,
+  requireRole('LANDLORD', 'ADMIN'),
+  async (req: AuthedRequest, res: Response) => {
+    const { userId, roomId, startDate, totalWarmRent, depositAmount, paymentDueDay, noticePeriodMonths } = req.body || {};
+
+    if (!userId || typeof userId !== 'string') return res.status(400).json({ error: 'userId ist erforderlich' });
+    if (!roomId || typeof roomId !== 'string') return res.status(400).json({ error: 'roomId ist erforderlich' });
+    if (!startDate || Number.isNaN(Date.parse(startDate))) return res.status(400).json({ error: 'startDate ist erforderlich' });
+    if (!Number.isFinite(Number(totalWarmRent)) || Number(totalWarmRent) <= 0) {
+      return res.status(400).json({ error: 'totalWarmRent muss eine positive Zahl sein' });
+    }
+    if (!Number.isFinite(Number(depositAmount)) || Number(depositAmount) < 0) {
+      return res.status(400).json({ error: 'depositAmount muss eine Zahl sein' });
+    }
+
+    const user = await prisma.user.findUnique({ where: { id: userId } });
+    if (!user) return res.status(404).json({ error: 'Mieter nicht gefunden' });
+
+    const room = await prisma.room.findUnique({ where: { id: roomId } });
+    if (!room) return res.status(404).json({ error: 'Zimmer nicht gefunden' });
+
+    const [activeForUser, activeForRoom] = await Promise.all([
+      prisma.contract.findFirst({ where: { userId, isActive: true } }),
+      prisma.contract.findFirst({ where: { roomId, isActive: true } }),
+    ]);
+    if (activeForUser) return res.status(409).json({ error: 'Mieter hat bereits einen aktiven Vertrag' });
+    if (activeForRoom) return res.status(409).json({ error: 'Zimmer ist bereits belegt' });
+
+    const [contract] = await prisma.$transaction([
+      prisma.contract.create({
+        data: {
+          userId,
+          roomId,
+          startDate: new Date(startDate),
+          totalWarmRent: Number(totalWarmRent),
+          depositAmount: Number(depositAmount),
+          paymentDueDay: Number.isFinite(Number(paymentDueDay)) ? Number(paymentDueDay) : 3,
+          noticePeriodMonths: Number.isFinite(Number(noticePeriodMonths)) ? Number(noticePeriodMonths) : 3,
+          isActive: true,
+        },
+        select: CONTRACT_DOCUMENTS_SELECT,
+      }),
+      prisma.user.update({ where: { id: userId }, data: { roomId } }),
+      prisma.room.update({ where: { id: roomId }, data: { status: 'OCCUPIED' } }),
+    ]);
+
+    res.status(201).json({ contract });
+  },
+);

web-dashboard/index.html

@@ -2882,14 +2882,17 @@
     if (!isLandlord) { section.style.display = 'none'; return; }
     section.style.display = 'block';
     try {
-      const data = await apiFetch('/contracts/archive');
+      const [archiveData, roomsData] = await Promise.all([
-      renderContractArchive(data.contracts);
+        apiFetch('/contracts/archive'),
+        apiFetch('/contracts/vacant-rooms'),
+      ]);
+      renderContractArchive(archiveData.contracts, roomsData.rooms);
     } catch (err) {
       console.error('[contracts] Archiv laden fehlgeschlagen:', err.message);
     }
   }
 
-  function renderContractArchive(contracts) {
+  function renderContractArchive(contracts, vacantRooms) {
     const list = document.getElementById('contractArchiveList');
     list.innerHTML = '';
     if (!contracts.length) {
@@ -2898,6 +2901,10 @@
     }
     contracts.forEach(c => {
       const row = el('div', 'ticket-row');
+      row.style.flexDirection = 'column';
+      row.style.alignItems = 'stretch';
+      row.style.gap = '10px';
+
       const left = el('div');
       left.appendChild(el('div', 'title', `${c.user.fullName} · ${c.room.roomNumber}`));
       left.appendChild(el('div', 'meta-text',
@@ -2918,10 +2925,119 @@
         });
         row.appendChild(docWrap);
       }
+
+      row.appendChild(buildReactivateSection(c, vacantRooms));
+
       list.appendChild(row);
     });
   }
 
+  function buildReactivateSection(c, vacantRooms) {
+    const wrap = el('div');
+
+    const toggleBtn = document.createElement('button');
+    toggleBtn.type = 'button';
+    toggleBtn.className = 'btn-secondary';
+    toggleBtn.textContent = 'Wieder aufnehmen (neuer Vertrag)';
+
+    const formArea = el('div', 'contract-template-form');
+    formArea.style.display = 'none';
+    formArea.style.marginTop = '10px';
+
+    if (!vacantRooms.length) {
+      formArea.appendChild(el('span', 'meta-text', 'Kein freies Zimmer verfügbar.'));
+    } else {
+      const roomField = el('div', 'field');
+      roomField.style.minWidth = '150px';
+      roomField.appendChild(el('label', null, 'Zimmer'));
+      const roomSelect = document.createElement('select');
+      vacantRooms.forEach(r => {
+        const opt = document.createElement('option');
+        opt.value = r.id;
+        opt.textContent = r.roomNumber;
+        opt.dataset.baseRent = r.baseRent;
+        opt.dataset.utilityPauschal = r.utilityPauschal;
+        roomSelect.appendChild(opt);
+      });
+      roomField.appendChild(roomSelect);
+      formArea.appendChild(roomField);
+
+      const startField = el('div', 'field');
+      startField.style.minWidth = '150px';
+      startField.appendChild(el('label', null, 'Mietbeginn'));
+      const startInput = document.createElement('input');
+      startInput.type = 'date';
+      startField.appendChild(startInput);
+      formArea.appendChild(startField);
+
+      const rentField = el('div', 'field');
+      rentField.style.width = '130px';
+      rentField.appendChild(el('label', null, 'Warmmiete (€)'));
+      const rentInput = document.createElement('input');
+      rentInput.type = 'number';
+      rentInput.min = '0';
+      rentInput.step = '0.01';
+      const firstRoom = vacantRooms[0];
+      rentInput.value = (Number(firstRoom.baseRent) + Number(firstRoom.utilityPauschal)).toFixed(2);
+      rentField.appendChild(rentInput);
+      formArea.appendChild(rentField);
+
+      const depositField = el('div', 'field');
+      depositField.style.width = '130px';
+      depositField.appendChild(el('label', null, 'Kaution (€)'));
+      const depositInput = document.createElement('input');
+      depositInput.type = 'number';
+      depositInput.min = '0';
+      depositInput.step = '0.01';
+      depositInput.value = (Number(firstRoom.baseRent) * 3).toFixed(2);
+      depositField.appendChild(depositInput);
+      formArea.appendChild(depositField);
+
+      roomSelect.onchange = () => {
+        const opt = roomSelect.selectedOptions[0];
+        rentInput.value = (Number(opt.dataset.baseRent) + Number(opt.dataset.utilityPauschal)).toFixed(2);
+        depositInput.value = (Number(opt.dataset.baseRent) * 3).toFixed(2);
+      };
+
+      const submitBtn = document.createElement('button');
+      submitBtn.type = 'button';
+      submitBtn.className = 'btn-primary';
+      submitBtn.style.width = 'auto';
+      submitBtn.textContent = 'Neuen Vertrag anlegen';
+      submitBtn.onclick = () => reactivateTenant(c.user.id, {
+        roomId: roomSelect.value,
+        startDate: startInput.value,
+        totalWarmRent: rentInput.value,
+        depositAmount: depositInput.value,
+      }, submitBtn);
+      formArea.appendChild(submitBtn);
+    }
+
+    toggleBtn.onclick = () => {
+      formArea.style.display = formArea.style.display === 'none' ? 'flex' : 'none';
+    };
+
+    wrap.appendChild(toggleBtn);
+    wrap.appendChild(formArea);
+    return wrap;
+  }
+
+  async function reactivateTenant(userId, options, btn) {
+    if (!options.startDate) { alert('Bitte Mietbeginn angeben.'); return; }
+    btn.disabled = true;
+    btn.textContent = 'Legt an…';
+    try {
+      await apiFetch('/contracts/reactivate', { method: 'POST', body: JSON.stringify({ userId, ...options }) });
+      loadContractDocuments();
+      loadContractArchive();
+    } catch (err) {
+      alert(err.message);
+    } finally {
+      btn.disabled = false;
+      btn.textContent = 'Neuen Vertrag anlegen';
+    }
+  }
+
   function buildContractTemplateForm(c) {
     const form = el('div', 'contract-template-form');