Implements the "1-Klick-PDF-Export für Handwerker" requirement from
the ticketing module spec, which existed only as a schema stub
(HandoverProtocol.pdfUrl) with no actual generator anywhere in the
codebase. Adds a server-side PDF endpoint (pdfkit, no headless
browser needed) summarizing a ticket's category, priority, status,
room, reporter and description, plus a "PDF" button in the landlord
cockpit that downloads it via an authenticated blob fetch (the API
uses a Bearer token, not cookies, so a plain <a href> wouldn't carry
auth).
The seed's deleteMany() chain didn't cover Ticket (or other tables
that now reference User), so it started failing with a foreign key
violation once real ticket data existed. Rather than cascading the
delete (which would wipe real data on every container restart), seed
now only runs against an empty database and is a no-op otherwise.
ts-node resolved node_modules relative to the script path, so running
from prisma/seed.ts (outside backend/) never found bcryptjs or
@prisma/client in backend/node_modules — the seed silently failed on
every container start. Moving the script under backend/prisma/ fixes
resolution; also adds a missing .gitignore for node_modules.
