feat: add authentication and user management with Authentik integration

- Add PostgreSQL database with async SQLAlchemy
- Add Alembic migrations for schema management
- Add User, Role, UserPreferences, ApiKey models
- Add auth endpoints: /auth/me, /auth/users, /auth/users/sync-from-authentik
- Add token validation via Authentik userinfo endpoint
- Add bulk user sync from Authentik admin API
- Add database health check to diagnostics

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

alembic.ini

@@ -0,0 +1,68 @@
+# Alembic Configuration for Core-API
+#
+# Database migrations using async SQLAlchemy
+
+[alembic]
+# Path to migration scripts
+script_location = alembic
+
+# Template for migration file names
+file_template = %%(year)d%%(month).2d%%(day).2d_%%(hour).2d%%(minute).2d_%%(rev)s_%%(slug)s
+
+# Prepend sys.path with the project root
+prepend_sys_path = .
+
+# Timezone for revision creation date
+timezone = UTC
+
+# Max length of revision identifiers
+truncate_slug_length = 40
+
+# Set to 'true' to run in offline mode
+revision_environment = false
+
+# Set to 'true' for sqlalchemy.url to be from the environment
+# We use env.py to get the URL from config.py instead
+sqlalchemy.url =
+
+[post_write_hooks]
+# Black formatting on generated migration files
+# hooks = black
+# black.type = console_scripts
+# black.entrypoint = black
+# black.options = -l 100 REVISION_SCRIPT_FILENAME
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S