Feat: Add tag browser page at /tags with count-sorted tag list and library deep-link

- Extends GET /api/v1/tags with sort=count_desc and min_count query params
- New TagsComponent at /tags (public, no auth guard) shows all tags sorted by image count
- Clicking a tag navigates to /?tags=<name> for a pre-filtered library view
- LibraryComponent reads ?tags= query param on init to support deep-linking from tag browser
- Library header gains a "Browse tags" link to /tags for discoverability
- All 15 TDD tasks complete; ruff, ng lint, and ng build clean

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

api/tests/integration/conftest.py

@@ -1,19 +1,19 @@
 import os
-import pytest
+
 import pytest_asyncio
-from httpx import AsyncClient, ASGITransport
-from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker
+from httpx import ASGITransport, AsyncClient
+from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
 
 # Provide required settings for the test environment before any app imports resolve them
 os.environ.setdefault("JWT_SECRET_KEY", "test-secret-key-for-testing-only")
 os.environ.setdefault("OWNER_USERNAME", "testowner")
 os.environ.setdefault("OWNER_PASSWORD", "testpassword")
 
-from app.main import app
+from app.auth.jwt_provider import JWTAuthProvider
 from app.config import get_settings
 from app.database import Base
-from app.dependencies import get_db, get_storage, get_auth
-from app.auth.jwt_provider import JWTAuthProvider
+from app.dependencies import get_auth, get_db, get_storage
+from app.main import app
 
 # Bust the LRU cache so get_settings() picks up the env vars set above
 get_settings.cache_clear()
@@ -48,8 +48,8 @@ async def db_session(engine):
 
 @pytest_asyncio.fixture
 async def client(db_session):
-    from app.storage.s3_backend import S3StorageBackend
     from app.auth.noop import NoOpAuthProvider
+    from app.storage.s3_backend import S3StorageBackend
 
     storage = S3StorageBackend()
     auth = NoOpAuthProvider()