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>

frontend/src/App.tsx

@@ -2,6 +2,7 @@ import { Routes, Route, Navigate } from "react-router-dom";
 import LoginPage from "./pages/LoginPage";
 import RegisterPage from "./pages/RegisterPage";
 import DashboardPage from "./pages/DashboardPage";
+import ProfilePage from "./pages/ProfilePage";
 import LoginSuccessPage from "./pages/LoginSuccessPage";
 import RegisterSuccessPage from "./pages/RegisterSuccessPage";
 import { useAuth } from "./hooks/useAuth";
@@ -33,6 +34,14 @@ export default function App() {
           </PrivateRoute>
         }
       />
+      <Route
+        path="/profile"
+        element={
+          <PrivateRoute>
+            <ProfilePage />
+          </PrivateRoute>
+        }
+      />
     </Routes>
   );
 }