Merge feature/birthday-sync: sync DOB to umbral contacts on profile/settings change

C-01: sync_birthday_to_contacts now accepts (share_birthday, date_of_birth)
      directly — no internal re-query, no stale-read risk with autoflush.
W-01: Eliminated redundant User/Settings SELECTs inside the service.
W-02: Removed scalar_one() on User query (no longer queries internally).
W-03: Settings router only syncs when share_birthday value actually changes.
S-02: Added logger.info with rowcount for observability.

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

backend/app/routers/auth.py

@@ -25,6 +25,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy import select, func
 
 from app.database import get_db
+from app.services.connection import sync_birthday_to_contacts
 from app.models.user import User
 from app.models.session import UserSession
 from app.models.settings import Settings
@@ -686,6 +687,12 @@ async def update_profile(
         current_user.email = update_data["email"]
     if "date_of_birth" in update_data:
         current_user.date_of_birth = update_data["date_of_birth"]
+        settings_result = await db.execute(
+            select(Settings).where(Settings.user_id == current_user.id)
+        )
+        user_settings = settings_result.scalar_one_or_none()
+        share = user_settings.share_birthday if user_settings else False
+        await sync_birthday_to_contacts(db, current_user.id, share_birthday=share, date_of_birth=update_data["date_of_birth"])
     if "umbral_name" in update_data:
         current_user.umbral_name = update_data["umbral_name"]
 

backend/app/routers/settings.py

@@ -7,6 +7,7 @@ from app.models.settings import Settings
 from app.models.user import User
 from app.schemas.settings import SettingsUpdate, SettingsResponse
 from app.routers.auth import get_current_user, get_current_settings
+from app.services.connection import sync_birthday_to_contacts
 
 router = APIRouter()
 
@@ -78,6 +79,7 @@ async def get_settings(
 async def update_settings(
     settings_update: SettingsUpdate,
     db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
     current_settings: Settings = Depends(get_current_settings)
 ):
     """Update settings."""
@@ -91,9 +93,18 @@ async def update_settings(
         except ValueError as e:
             raise HTTPException(status_code=400, detail=str(e))
 
+    old_share_birthday = current_settings.share_birthday
+
     for key, value in update_data.items():
         setattr(current_settings, key, value)
 
+    if "share_birthday" in update_data and update_data["share_birthday"] != old_share_birthday:
+        await sync_birthday_to_contacts(
+            db, current_user.id,
+            share_birthday=update_data["share_birthday"],
+            date_of_birth=current_user.date_of_birth,
+        )
+
     await db.commit()
     await db.refresh(current_settings)
 

backend/app/services/connection.py

@@ -9,6 +9,7 @@ from datetime import date as date_type
 from types import SimpleNamespace
 from typing import Optional
 
+from sqlalchemy import update
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.models.person import Person
@@ -134,6 +135,25 @@ def create_person_from_connection(
     )
 
 
+
+async def sync_birthday_to_contacts(
+    db: AsyncSession,
+    user_id: int,
+    share_birthday: bool,
+    date_of_birth: Optional[date_type],
+) -> None:
+    """Sync user's DOB to all Person records where linked_user_id == user_id.
+    Caller passes resolved values — no internal re-query."""
+    new_birthday = date_of_birth if share_birthday else None
+
+    result = await db.execute(
+        update(Person)
+        .where(Person.linked_user_id == user_id)
+        .values(birthday=new_birthday)
+    )
+    logger.info("sync_birthday_to_contacts user_id=%s updated %s person(s)", user_id, result.rowcount)
+
+
 async def detach_umbral_contact(person: Person) -> None:
     """Convert an umbral contact back to a standard contact. Does NOT commit.