feat: integrate SvelteKit for seamless navigation and improved data loading

specs/004-integrate-svelte-kit/contracts/api.md

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+# API Contracts: SvelteKit Frontend
+
+The SvelteKit frontend will interact with the following existing backend API endpoints.
+
+## Settings API (`/api/settings`)
+
+### Get All Settings
+- **Endpoint**: `GET /api/settings/`
+- **Response**: `AppConfig` (JSON)
+- **Usage**: Load initial configuration for the application.
+
+### Update Global Settings
+- **Endpoint**: `PATCH /api/settings/global`
+- **Request Body**: `GlobalSettings` (JSON)
+- **Response**: `GlobalSettings` (JSON)
+- **Usage**: Save changes to global settings.
+
+### List Environments
+- **Endpoint**: `GET /api/settings/environments`
+- **Response**: `List[Environment]` (JSON)
+- **Usage**: Display configured Superset environments.
+
+### Add Environment
+- **Endpoint**: `POST /api/settings/environments`
+- **Request Body**: `Environment` (JSON)
+- **Response**: `Environment` (JSON)
+- **Usage**: Create a new environment configuration.
+
+### Update Environment
+- **Endpoint**: `PUT /api/settings/environments/{id}`
+- **Request Body**: `Environment` (JSON)
+- **Response**: `Environment` (JSON)
+- **Usage**: Modify an existing environment.
+
+### Delete Environment
+- **Endpoint**: `DELETE /api/settings/environments/{id}`
+- **Response**: `{"message": "..."}`
+- **Usage**: Remove an environment.
+
+### Test Connection
+- **Endpoint**: `POST /api/settings/environments/{id}/test`
+- **Response**: `{"status": "success/error", "message": "..."}`
+- **Usage**: Verify connectivity to a Superset instance.
+
+## Plugins API (`/api/plugins`)
+
+### List Plugins
+- **Endpoint**: `GET /api/plugins/`
+- **Response**: `List[PluginConfig]` (JSON)
+- **Usage**: Display available plugins on the Dashboard.
+
+## Tasks API (`/api/tasks`)
+*(Inferred from file list, used for running plugin tasks)*
+
+### List Tasks
+- **Endpoint**: `GET /api/tasks/`
+- **Usage**: Show active or historical tasks.
+
+### Run Task
+- **Endpoint**: `POST /api/tasks/{plugin_id}`
+- **Usage**: Execute a plugin-specific task.