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/profile.py

@@ -0,0 +1,44 @@
+from datetime import date, datetime
+
+from pydantic import BaseModel, field_validator
+
+from app.core.sanitize import sanitize_str, validate_date_of_birth, validate_phone
+
+
+class ProfileRead(BaseModel):
+    id: str
+    user_id: str
+    phone: str | None
+    date_of_birth: date | None
+    position: str | None
+    address: str | None
+    updated_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class ProfileUpdate(BaseModel):
+    phone: str | None = None
+    date_of_birth: date | None = None
+    position: str | None = None
+    address: str | None = None
+
+    @field_validator("phone", mode="before")
+    @classmethod
+    def clean_phone(cls, v: str | None) -> str | None:
+        return validate_phone(v)
+
+    @field_validator("position", mode="before")
+    @classmethod
+    def clean_position(cls, v: str | None) -> str | None:
+        return sanitize_str(v, max_len=128)
+
+    @field_validator("address", mode="before")
+    @classmethod
+    def clean_address(cls, v: str | None) -> str | None:
+        return sanitize_str(v, max_len=255)
+
+    @field_validator("date_of_birth", mode="after")
+    @classmethod
+    def clean_dob(cls, v: date | None) -> date | None:
+        return validate_date_of_birth(v)