refactor(auth): implement token-based authentication with JWT parsing

- Replace authStore with tokenService for authentication management
- Add JWT parsing utility to extract user info from tokens
- Update login flow to use cookie-based token storage
- Modify logout to properly clear auth state and cookies
- Integrate user data into page context for SSR compatibility
- Remove deprecated authStore and related localStorage logic
- Add cookie constants for consistent token handling
- Implement server-side token validation in hooks
- Update HTTP client to use token from cookies instead of store
- Refactor error handling to use unified ApiError class
- Replace manual redirect logic with resolved paths
- Improve type safety with explicit user and auth interfaces
- Add toast notifications for login/logout feedback
- Remove unused sidebar store and related UI logic
- Migrate theme handling to use cookies and context
- Update icon definitions and component references
- Clean up legacy code and unused imports

src/lib/stores/theme.svelte.ts

@@ -0,0 +1,16 @@
+import type { DaisyUIThemeID } from '$lib/types/theme.ts';
+
+export class ThemeState {
+	theme: DaisyUIThemeID = $state('dark');
+
+	constructor(initialTheme = 'dark' as DaisyUIThemeID) {
+		this.theme = initialTheme;
+	}
+
+	setTheme(theme: DaisyUIThemeID) {
+		this.theme = theme;
+	}
+}
+
+
+export const THEME_KEY = Symbol('THEME');