feat(security): JWT required on every API route, gated dev fallback, role checks

- main.py: global get_current_user dependency on all routers except
  /auth/login and /health; prod fail-fast startup guard rejects wildcard
  CORS, default credentials, DEV_LOGIN_ENABLED
- inventory/pm: X-User-Role header identity fallback now only active when
  PROCUREMENT_DEV_LOGIN_ENABLED=true (was unconditional in production)
- item_decisions writes + attachment deletes: require_role(
  procurement_manager, admin) — require_role was defined but never used
- config.py: ENVIRONMENT flag, comma-separated CORS_ORIGINS, no default
  Casdoor client secret/admin password, DEV_LOGIN_ENABLED=false
- frontend: authenticated file downloads (Bearer + blob) — <a href> links
  cannot send the token; FileList/QuoteDetail/AcceptModal/EditModal/
  PurchaseHistory converted; DEV_LOGIN_ENABLED build arg defaults false
- smoke tests authenticate via POST /auth/login (SMOKE_USER/SMOKE_PASSWORD)
- traefik: security headers, API rate limit, 12MB body cap (prod overlay)
- nginx client_max_body_size aligned to 12MB

backend/requirements.txt

@@ -10,3 +10,10 @@ minio>=7.2.0
 # v2.6 — Casdoor JWT auth
 pyjwt[crypto]>=2.8.0
 httpx>=0.27.0
+
+# Casdoor seeding — bcrypt password hashes (never plaintext)
+bcrypt>=4.1.0
+
+# Observability — metrics + Sentry/GlitchTip exception capture
+prometheus-fastapi-instrumentator>=7.0.0
+sentry-sdk[fastapi]>=2.0.0