step 9 complete: auth middleware, tier-aware rate limiter, and response sanitizer

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

app/api/middleware/__init__.py

@@ -0,0 +1,19 @@
+"""API middleware package.
+
+Exports the three middleware components introduced in Step 9:
+  - Auth:        ``get_current_user`` FastAPI dependency + ``oauth2_scheme``
+  - Rate limit:  ``TierRateLimitMiddleware`` + ``limiter`` (slowapi Limiter)
+  - Sanitizer:   ``SanitizerMiddleware``
+"""
+
+from app.api.middleware.auth import get_current_user, oauth2_scheme
+from app.api.middleware.rate_limit import TierRateLimitMiddleware, limiter
+from app.api.middleware.sanitizer import SanitizerMiddleware
+
+__all__ = [
+    "get_current_user",
+    "oauth2_scheme",
+    "TierRateLimitMiddleware",
+    "limiter",
+    "SanitizerMiddleware",
+]