feat: implement plugin architecture and application settings with Svelte UI

- Added plugin base and loader for backend extensibility
- Implemented application settings management with config persistence
- Created Svelte-based frontend with Dashboard and Settings pages
- Added API routes for plugins, tasks, and settings
- Updated documentation and specifications
- Improved project structure and developer tools

backend/src/core/config_models.py

@@ -0,0 +1,36 @@
+# [DEF:ConfigModels:Module]
+# @SEMANTICS: config, models, pydantic
+# @PURPOSE: Defines the data models for application configuration using Pydantic.
+# @LAYER: Core
+# @RELATION: READS_FROM -> config.json
+# @RELATION: USED_BY -> ConfigManager
+
+from pydantic import BaseModel, Field
+from typing import List, Optional
+
+# [DEF:Environment:DataClass]
+# @PURPOSE: Represents a Superset environment configuration.
+class Environment(BaseModel):
+    id: str
+    name: str
+    url: str
+    username: str
+    password: str  # Will be masked in UI
+    is_default: bool = False
+# [/DEF:Environment]
+
+# [DEF:GlobalSettings:DataClass]
+# @PURPOSE: Represents global application settings.
+class GlobalSettings(BaseModel):
+    backup_path: str
+    default_environment_id: Optional[str] = None
+# [/DEF:GlobalSettings]
+
+# [DEF:AppConfig:DataClass]
+# @PURPOSE: The root configuration model containing all application settings.
+class AppConfig(BaseModel):
+    environments: List[Environment] = []
+    settings: GlobalSettings
+# [/DEF:AppConfig]
+
+# [/DEF:ConfigModels]