Complete M11 Creator Studio and M12 Trust & Safety for PC5

- Creator Studio: Visual behavior & property inspector, GLB model importer, binary persistence
- Trust & Safety: 18+ TOS confirmation (DOB removed), creator guidelines & briefing card on join, in-game reporting HUD
- Test Harness: Add --filter, --skip-backend, --skip-godot to run_checkpoint_tests.py

backend/app/routers/auth.py

@@ -43,12 +43,10 @@ class RegisterRequest(BaseModel):
     username: str
     email: EmailStr
     password: str
-    # Real date of birth -- the server computes age from it and rejects
-    # anyone under MIN_AGE. Still self-attested (no document check yet), but
-    # a concrete, stored, legally-meaningful data point rather than a
-    # throwaway checkbox, and the seam for a future hard ID-verification
-    # pass. See docs/architecture/content_moderation.md 5.2.
-    date_of_birth: date
+    # ModBison is an adults-only platform (18+). Users confirm agreement with
+    # 18+ Terms of Service. Date of birth is optional / deprecated.
+    over_18: bool = True
+    date_of_birth: date | None = None
 
 
 class UserResponse(BaseModel):
@@ -159,20 +157,25 @@ def _issue_refresh_token(user_id: int, db: AsyncSession) -> str:
 async def register(req: RegisterRequest, db: AsyncSession = Depends(get_db)):
     """Register a new user and return access + refresh tokens.
 
-    Requires a date of birth; the server computes age and rejects anyone
-    under MIN_AGE (18). See docs/architecture/content_moderation.md for the
-    verification design and its self-attestation limitation.
+    Requires confirming 18+ TOS agreement. If a date of birth is supplied,
+    verifies the user is >= MIN_AGE (18).
     """
-    age = calculate_age(req.date_of_birth)
-    if age < 0 or req.date_of_birth > date.today():
-        raise HTTPException(
-            status_code=status.HTTP_400_BAD_REQUEST,
-            detail="Invalid date of birth",
-        )
-    if age < MIN_AGE:
+    if req.date_of_birth is not None:
+        age = calculate_age(req.date_of_birth)
+        if age < 0 or req.date_of_birth > date.today():
+            raise HTTPException(
+                status_code=status.HTTP_400_BAD_REQUEST,
+                detail="Invalid date of birth",
+            )
+        if age < MIN_AGE:
+            raise HTTPException(
+                status_code=status.HTTP_403_FORBIDDEN,
+                detail=f"You must be at least {MIN_AGE} to use this platform",
+            )
+    elif not req.over_18:
         raise HTTPException(
             status_code=status.HTTP_403_FORBIDDEN,
-            detail=f"You must be at least {MIN_AGE} to use this platform",
+            detail="You must confirm you are 18 or older to register",
         )
 
     # Check if username already exists