feat: add dashboard API with quick links and widgets

- Dashboard domain with Quick Links CRUD + reorder endpoints
- Dashboard widgets management endpoints
- Database migrations for quick_links and dashboard_widgets tables
- Static file controller for Organizr widgets
- Default local user when OIDC is disabled
- Domain-based architecture refactor (src/domains/, src/shared/)
- Test suite updated for new structure (285 tests passing)

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

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

src/shared/__init__.py

@@ -0,0 +1,50 @@
+"""
+Shared utilities for Core-API
+
+Contains common base classes, configuration, database, logging utilities,
+and API clients used across all domains.
+"""
+from src.shared.config import get_settings, Settings
+from src.shared.database import Base, get_database, get_async_session
+from src.shared.logging import get_logger, setup_logging
+from src.shared.base import BaseController, BaseSchema
+from src.shared.security import initialize_oidc
+
+# Re-export clients for convenience
+from src.shared.clients import (
+    PortainerClient,
+    get_portainer_client,
+    NPMClient,
+    get_npm_client,
+    HomeAssistantClient,
+    get_homeassistant_client,
+    AuthentikClient,
+    get_authentik_client,
+)
+
+__all__ = [
+    # Config
+    "get_settings",
+    "Settings",
+    # Database
+    "Base",
+    "get_database",
+    "get_async_session",
+    # Logging
+    "get_logger",
+    "setup_logging",
+    # Base classes
+    "BaseController",
+    "BaseSchema",
+    # Security
+    "initialize_oidc",
+    # Clients
+    "PortainerClient",
+    "get_portainer_client",
+    "NPMClient",
+    "get_npm_client",
+    "HomeAssistantClient",
+    "get_homeassistant_client",
+    "AuthentikClient",
+    "get_authentik_client",
+]