Add user bug reporting with admin triage (open/read/resolved)

Turns the /report-bug placeholder into a real form (POST /bug-reports,
optionally attributed to the logged-in user) and adds a "Segnalazioni bug"
section to /admin to view and triage them. A logged-in reporter can also
check their own report's status via GET /bug-reports/mine, since anonymous
submissions have no user to show a history to.

Status is a three-state lifecycle (open -> read -> resolved) rather than a
plain boolean, so an admin can acknowledge a report distinctly from actually
fixing it. The schema went through two migrations because the first one
(add bug_reports table) had already been applied against the running
instance with a `resolved` boolean before the three-state design was
decided, so a follow-up migration backfills it into `status` instead of
rewriting already-applied history.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/main.py

@@ -15,6 +15,7 @@ import app.rounds.confirmation  # noqa: F401  (registers the "payout" confirmati
 import app.withdrawals.confirmation  # noqa: F401  (registers the "withdrawal" confirmation handler)
 from app.api.routes.admin import router as admin_router
 from app.api.routes.bets import router as bets_router
+from app.api.routes.bug_reports import router as bug_reports_router
 from app.api.routes.qr import router as qr_router
 from app.api.routes.rounds import router as rounds_router
 from app.api.routes.users import router as users_router
@@ -99,6 +100,7 @@ app.include_router(users_router)
 app.include_router(bets_router)
 app.include_router(withdrawals_router)
 app.include_router(admin_router)
+app.include_router(bug_reports_router)
 app.include_router(qr_router)
 app.include_router(rounds_router)