refactor: reorganize directory structure into src/

Move all source code directories into src/ for cleaner project structure:
- pages/, components/, utils/, config/, providers/, types/, lib/, assets/, entrypoints/ → src/
- Use WXT srcDir config to resolve @/ alias to src/
- Update tsconfig, vitest, eslint, tailwind configs
- Remove scattered README.md files from subdirectories
- Update documentation (AGENTS.md, CODING_STANDARDS.md, README.md)
- Fix pre-existing lint error in RouterProvider.tsx

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/config/__tests__/features.test.ts

@@ -0,0 +1,131 @@
+import { describe, expect, it } from 'vitest';
+import {
+  FEATURES,
+  getAllFeatureKeys,
+  getDefaultPageOrder,
+  getDefaultVisibleFeatureKeys,
+  getFeatureByKey,
+} from '@/config/features';
+
+describe('features', () => {
+  describe('FEATURES', () => {
+    it('should have 11 features defined', () => {
+      expect(FEATURES).toHaveLength(11);
+    });
+
+    it('should have all required properties for each feature', () => {
+      FEATURES.forEach((feature) => {
+        expect(feature).toHaveProperty('key');
+        expect(feature).toHaveProperty('labelKey');
+        expect(feature).toHaveProperty('descriptionKey');
+        expect(feature).toHaveProperty('defaultVisible');
+        expect(feature).toHaveProperty('components');
+        expect(typeof feature.key).toBe('string');
+        expect(typeof feature.labelKey).toBe('string');
+        expect(typeof feature.descriptionKey).toBe('string');
+        expect(typeof feature.defaultVisible).toBe('boolean');
+        expect(typeof feature.components).toBe('object');
+        expect(feature.components).toHaveProperty('popup');
+        expect(feature.components).toHaveProperty('sidepanel');
+        expect(feature.components).toHaveProperty('tab');
+
+        // Optional UI properties for non-hidden features
+        if (feature.key !== 'dashboard') {
+          expect(feature).toHaveProperty('icon');
+          expect(feature).toHaveProperty('themeColorKey');
+          expect(typeof feature.themeColorKey).toBe('string');
+        }
+      });
+    });
+
+    it('should have unique keys for each feature', () => {
+      const keys = FEATURES.map((f) => f.key);
+      const uniqueKeys = new Set(keys);
+      expect(uniqueKeys.size).toBe(keys.length);
+    });
+  });
+
+  describe('getFeatureByKey', () => {
+    it('should return dashboard feature', () => {
+      const feature = getFeatureByKey('dashboard');
+      expect(feature).toBeDefined();
+      expect(feature?.key).toBe('dashboard');
+      expect(feature?.labelKey).toBe('dashboard_title');
+    });
+
+    it('should return timestamp feature', () => {
+      const feature = getFeatureByKey('timestamp');
+      expect(feature).toBeDefined();
+      expect(feature?.key).toBe('timestamp');
+      expect(feature?.labelKey).toBe('timestamp_title');
+      expect(feature?.themeColorKey).toBeDefined();
+    });
+
+    it('should return storageCleaner feature', () => {
+      const feature = getFeatureByKey('storageCleaner');
+      expect(feature).toBeDefined();
+      expect(feature?.key).toBe('storageCleaner');
+      expect(feature?.labelKey).toBe('storageCleaner_title');
+    });
+
+    it('should return undefined for invalid key', () => {
+      const feature = getFeatureByKey('invalid' as any);
+      expect(feature).toBeUndefined();
+    });
+  });
+
+  describe('getDefaultVisibleFeatureKeys', () => {
+    it('should return only visible features', () => {
+      const visibleKeys = getDefaultVisibleFeatureKeys();
+      visibleKeys.forEach((key) => {
+        const feature = getFeatureByKey(key);
+        expect(feature?.defaultVisible).toBe(true);
+      });
+    });
+
+    it('should include dashboard, timestamp, storageCleaner, qrCode', () => {
+      const visibleKeys = getDefaultVisibleFeatureKeys();
+      expect(visibleKeys).toContain('dashboard');
+      expect(visibleKeys).toContain('timestamp');
+      expect(visibleKeys).toContain('storageCleaner');
+      expect(visibleKeys).toContain('qrCode');
+    });
+  });
+
+  describe('getAllFeatureKeys', () => {
+    it('should return all feature keys', () => {
+      const allKeys = getAllFeatureKeys();
+      expect(allKeys).toHaveLength(11);
+      expect(allKeys).toContain('dashboard');
+      expect(allKeys).toContain('timestamp');
+      expect(allKeys).toContain('storageCleaner');
+      expect(allKeys).toContain('qrCode');
+      expect(allKeys).toContain('textStatistics');
+      expect(allKeys).toContain('jwt');
+      expect(allKeys).toContain('jsonDiff');
+      expect(allKeys).toContain('base64Converter');
+      expect(allKeys).toContain('markdownToHtml');
+      expect(allKeys).toContain('htmlToMarkdown');
+      expect(allKeys).toContain('rightClickRestorer');
+    });
+  });
+
+  describe('getDefaultPageOrder', () => {
+    it('should exclude dashboard from page order', () => {
+      const pageOrder = getDefaultPageOrder();
+      expect(pageOrder).not.toContain('dashboard');
+    });
+
+    it('should include timestamp, storageCleaner, qrCode in page order', () => {
+      const pageOrder = getDefaultPageOrder();
+      expect(pageOrder).toContain('timestamp');
+      expect(pageOrder).toContain('storageCleaner');
+      expect(pageOrder).toContain('qrCode');
+    });
+
+    it('should have 10 items in page order', () => {
+      const pageOrder = getDefaultPageOrder();
+      expect(pageOrder).toHaveLength(10);
+    });
+  });
+});