docs(dev): integrate rest of the documentation

docs/Developer Guide/Developer Guide/Architecture/Frontend.md

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+# Frontend
+### Application Entry Point
+
+**Desktop:** `apps/client/src/desktop.ts` **Web:** `apps/client/src/index.ts`
+
+### Service Layer
+
+Located at: `apps/client/src/services/`
+
+Key services:
+
+*   `froca.ts` - Frontend cache
+*   `server.ts` - API communication
+*   `ws.ts` - WebSocket connection
+*   `tree_service.ts` - Note tree management
+*   `note_context.ts` - Active note tracking
+*   `protected_session.ts` - Encryption key management
+*   `link.ts` - Note linking and navigation
+*   `export.ts` - Note export functionality
+
+### UI Components
+
+**Component Locations:**
+
+*   `widgets/containers/` - Layout containers
+*   `widgets/buttons/` - Toolbar buttons
+*   `widgets/dialogs/` - Modal dialogs
+*   `widgets/ribbon_widgets/` - Tab widgets
+*   `widgets/type_widgets/` - Note type editors
+
+### Event System
+
+**Application Events:**
+
+```typescript
+// Subscribe to events
+appContext.addBeforeUnloadListener(() => {
+    // Cleanup before page unload
+})
+
+// Trigger events
+appContext.trigger('noteTreeLoaded')
+```
+
+**Note Context Events:**
+
+```typescript
+// NoteContextAwareWidget automatically receives:
+- noteSwitched()
+- noteChanged()
+- refresh()
+```
+
+### State Management
+
+Trilium uses **custom state management** rather than Redux/MobX:
+
+*   `note_context.ts` - Active note and context
+*   `froca.ts` - Entity cache
+*   Component local state
+*   URL parameters for shareable state