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

reproduce_issue.py

@@ -0,0 +1,21 @@
+import sys
+import os
+from pathlib import Path
+
+# Add root to sys.path
+sys.path.append(os.getcwd())
+
+try:
+    from backend.src.core.plugin_loader import PluginLoader
+except ImportError as e:
+    print(f"Failed to import PluginLoader: {e}")
+    sys.exit(1)
+
+plugin_dir = Path("backend/src/plugins").absolute()
+print(f"Plugin dir: {plugin_dir}")
+
+loader = PluginLoader(str(plugin_dir))
+configs = loader.get_all_plugin_configs()
+print(f"Loaded plugins: {len(configs)}")
+for config in configs:
+    print(f" - {config.id}")