Add profile feature, input sanitization, and stronger security checks

Backend:
- app/core/sanitize.py: shared sanitize_str, normalize_email, validate_phone,
  validate_date_of_birth — applied to every user-supplied DB-bound input
- app/schemas/user.py: sanitize full_name, normalize email on UserCreate
- app/models/profile.py: profiles table (position, phone, dob, address, updated_at)
- app/models/user.py: Profile back-ref, is_superuser admin-role comment
- app/schemas/profile.py: ProfileRead/ProfileUpdate with full sanitization
- app/routers/profile.py: GET+PUT /api/profile/me (lazy profile creation)
- app/main.py: register /api/profile router
- alembic migration 676084df61d1: create profiles table

Frontend:
- components/Nav.tsx: shared nav (Dashboard | Profile | Logout)
- pages/ProfilePage.tsx: profile view + inline edit form with error handling
- pages/DashboardPage.tsx: use Nav component
- api/client.ts: ProfileData type, getProfile, updateProfile
- App.tsx: /profile private route

Security:
- scripts/security_check.py: tighter SQL injection patterns (f-string/format/%
  in execute/query/text()), new SANIT category for raw request→DB patterns

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

TODO.md

@@ -1,5 +1,11 @@
 # TODO
 
+## Frontend features
+
+- [x] **Logout button** — visible when logged in, clears token and redirects to `/login`
+- [x] **Profile page** (`/profile`) — shows personal information for the logged-in user
+- [x] **Edit & save profile** — form to update personal details, stored in a dedicated `profiles` table (separate from `users`, same PostgreSQL container)
+
 ## Infrastructure
 
 - [x] **Rootless containers** — run backend and frontend containers as non-root users (add `USER` directive to Dockerfiles, map UID/GID appropriately)