feat: add web UI with login, CRUD, admin, and API key management

- Add login page with JWT authentication
- Add dashboard with stats and quick actions
- Add links management page (full CRUD with search)
- Add collections management page
- Add API key management page with copy-to-clipboard
- Add admin user management page (admin only)
- Fix UUID type mismatches across all endpoints
- Add updated_at column to api_keys and audit_log in schema.sql
- Fix DB_PASSWORD default in docker-compose.yml
- Add PyJWT to requirements.txt
- Fix API docs URL (/docs instead of /api/docs)
- Improve JS error handling (show actual messages)
- Rewrite conftest.py with proper DB lifecycle management
- Add 42 new integration tests (84 total, all passing)
  - test_admin.py: 15 tests for admin endpoints
  - test_auth_extended.py: 9 tests for API key CRUD
  - test_tags.py: 12 tests for tag endpoints
  - test_sync.py: 6 tests for sync endpoints

LinkSyncServer/tests/conftest.py

@@ -1,32 +1,88 @@
 """
 LinkSyncServer - Test Configuration
+
+Database lifecycle:
+- pytest_configure: Creates fresh test database before any tests run
+- pytest_unconfigure: Destroys test database after all tests complete
+- Per-test: Transaction rollback ensures test isolation
 """
 
+import os
 import pytest
 from fastapi.testclient import TestClient
-from sqlalchemy import create_engine
+from sqlalchemy import create_engine, event
 from sqlalchemy.orm import sessionmaker
+from sqlalchemy.pool import StaticPool
 
-from models.base import Base, get_engine
+from models.base import Base
+import models.base
 
 
-SQLALCHEMY_DATABASE_URL = "sqlite:///test_linksync.db"
-engine = create_engine(SQLALCHEMY_DATABASE_URL, connect_args={"check_same_thread": False})
-TestingSessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+TEST_DATABASE_URL = "sqlite:///test_linksync.db"
+
+
+def pytest_configure(config):
+    """Called before any tests run. Creates fresh test database."""
+    if os.path.exists("test_linksync.db"):
+        os.remove("test_linksync.db")
+
+    test_engine = create_engine(
+        TEST_DATABASE_URL,
+        connect_args={"check_same_thread": False},
+        poolclass=StaticPool,
+    )
+    Base.metadata.create_all(bind=test_engine)
+
+    # Override the module-level get_engine to return our test engine
+    original_get_engine = models.base.get_engine
+    original_get_session = models.base.get_session
+
+    def test_get_engine():
+        return test_engine
+
+    def test_get_session():
+        Session = sessionmaker(bind=test_engine)
+        return Session()
+
+    models.base.get_engine = test_get_engine
+    models.base.get_session = test_get_session
+
+    # Store originals for cleanup
+    config._test_engine = test_engine
+    config._original_get_engine = original_get_engine
+    config._original_get_session = original_get_session
+
+
+def pytest_unconfigure(config):
+    """Called after all tests complete. Destroys test database."""
+    # Restore original functions
+    if hasattr(config, "_original_get_engine"):
+        models.base.get_engine = config._original_get_engine
+        models.base.get_session = config._original_get_session
+
+    # Drop all tables
+    if hasattr(config, "_test_engine"):
+        Base.metadata.drop_all(bind=config._test_engine)
+        config._test_engine.dispose()
+
+    # Remove the test database file
+    if os.path.exists("test_linksync.db"):
+        os.remove("test_linksync.db")
 
 
 @pytest.fixture(scope="session")
-def test_engine():
-    Base.metadata.create_all(bind=engine)
-    yield engine
-    Base.metadata.drop_all(bind=engine)
+def test_engine(pytestconfig):
+    """Provides the test engine for direct database access in tests."""
+    return pytestconfig._test_engine
 
 
 @pytest.fixture
 def db_session(test_engine):
+    """Provides a transactional session that rolls back after each test."""
     connection = test_engine.connect()
     transaction = connection.begin()
-    session = TestingSessionLocal(bind=connection)
+    Session = sessionmaker(bind=connection)
+    session = Session()
 
     yield session
 
@@ -37,6 +93,7 @@ def db_session(test_engine):
 
 @pytest.fixture
 def client():
+    """Provides a TestClient with the test database already configured."""
     from app import app
     with TestClient(app) as c:
         yield c