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>

backend/app/schemas/user.py

@@ -2,6 +2,8 @@ import re
 
 from pydantic import BaseModel, EmailStr, field_validator
 
+from app.core.sanitize import normalize_email, sanitize_str
+
 # Common words that must not appear as whole words inside a password.
 # Checked case-insensitively with word boundaries.
 _FORBIDDEN_WORDS = {
@@ -45,6 +47,16 @@ class UserCreate(BaseModel):
     password: str
     full_name: str | None = None
 
+    @field_validator("email", mode="before")
+    @classmethod
+    def normalize_email_field(cls, v: str) -> str:
+        return normalize_email(v)
+
+    @field_validator("full_name", mode="before")
+    @classmethod
+    def sanitize_full_name(cls, v: str | None) -> str | None:
+        return sanitize_str(v, max_len=128)
+
     @field_validator("password")
     @classmethod
     def password_strength(cls, v: str) -> str: