step 11 complete: billing service and tier manager

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

app/api/routes/backup.py

@@ -16,6 +16,7 @@ from typing import Any
 from fastapi import APIRouter, Depends, Header, HTTPException, Request, Response, status
 
 from app.api.deps import get_current_user
+from app.billing.tier_manager import tier_manager
 from app.schemas import BackupMetadata, UserProfile
 from app.storage.blob_store import BlobStore
 from app.storage.encryption import reject_if_tampered
@@ -27,32 +28,11 @@ _blob_store = BlobStore()
 # In-memory backup metadata — replaced by PostgreSQL backup_metadata table in Step 12
 _backups: dict[str, list[dict[str, Any]]] = {}  # user_id → list of backup records
 
-# TODO(Step11/12): replace with TierManager.check_quota(user_id)
-_TIER_BACKUP_LIMITS_GB: dict[str, int] = {
-    "free": 0,
-    "pro": 5,
-    "power": 25,
-    "team": -1,  # unlimited
-}
 
-
-def _check_backup_quota(user_id: str, tier: str, size_bytes: int) -> None:
+def _check_backup_quota(user_id: str, size_bytes: int) -> None:
     """Raise HTTP 402 if the upload would exceed the tier's backup limit."""
-    limit_gb = _TIER_BACKUP_LIMITS_GB.get(tier, 0)
-    if limit_gb == 0:
-        raise HTTPException(
-            status_code=status.HTTP_402_PAYMENT_REQUIRED,
-            detail="Backup is not available on the free tier",
-        )
-    if limit_gb == -1:
-        return  # unlimited
-    limit_bytes = limit_gb * 1024**3
-    used = sum(b["size_bytes"] for b in _backups.get(user_id, []))
-    if used + size_bytes > limit_bytes:
-        raise HTTPException(
-            status_code=status.HTTP_402_PAYMENT_REQUIRED,
-            detail=f"Backup quota exceeded for tier '{tier}'",
-        )
+    current = sum(b["size_bytes"] for b in _backups.get(user_id, []))
+    tier_manager.enforce_backup_quota(user_id, current_bytes=current, additional_bytes=size_bytes)
 
 
 @router.put("")
@@ -69,7 +49,7 @@ async def upload_backup(
     """
     blob = await request.body()
     reject_if_tampered(blob, x_backup_checksum)
-    _check_backup_quota(current_user.id, current_user.tier, len(blob))
+    _check_backup_quota(current_user.id, len(blob))
 
     s3_key = await _blob_store.upload(
         current_user.id, "backup", str(x_backup_timestamp), blob, x_backup_checksum