Add Projects, Milestones, RAG auto-inject, push notifications, PWA, tag normalisation

## Projects & Milestones (Phases A + G)
- New models: Project, Milestone (Project → Milestone → Task hierarchy)
- notes table: project_id + milestone_id FKs; parent_id FK constraint activated
- Migrations: 0017 (projects), 0018 (push_subscriptions), 0019 (events), 0020 (milestones)
- Services: projects.py, milestones.py (CRUD + progress tracking)
- Routes: /api/projects + /api/projects/<id>/milestones
- LLM tools: create/list/get/update project; create/list milestone; project + milestone + parent_task params on note/task tools
- Frontend: ProjectListView (stacked milestone bars), ProjectView (milestone-grouped kanban), ProjectSelector, MilestoneSelector, NoteEditorView + TaskEditorView updated

## RAG Auto-injection (Phase B)
- Notes ≥0.60 cosine similarity auto-injected into system prompt (max 3, 800 chars each)
- excluded_note_ids param; ChatView "Auto-included" sidebar section

## Summarisation improvements (Phase C)
- Threshold 20→30, keep-recent 6→8, max_tokens 200→400
- Two-pass summarisation for histories >50 messages

## Browser push notifications (Phase E)
- PushSubscription model + migration; pywebpush dependency
- /api/push routes; VAPID config; fire-and-forget on generation complete
- Frontend: sw.js, push store, Settings toggle

## PWA manifest (Phase F)
- manifest.json, Apple meta tags, service worker registration in main.ts

## Tag normalisation
- All tags lowercased + deduplicated at backend (create_note/update_note) and frontend (TagInput sanitize)
- Note/Task types gain project_id + milestone_id fields; store signatures updated

## CalDAV
- Radicale embedded server reverted; back to user-configured external CalDAV

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/public/sw.js

@@ -0,0 +1,35 @@
+// Service Worker for push notifications and PWA support
+self.addEventListener('push', event => {
+  if (!event.data) return;
+  const data = event.data.json();
+  event.waitUntil(
+    self.registration.showNotification(data.title || 'Fabled Assistant', {
+      body: data.body || '',
+      icon: '/favicon.ico',
+      badge: '/favicon.ico',
+      data: { url: data.url || '/' },
+    })
+  );
+});
+
+self.addEventListener('notificationclick', event => {
+  event.notification.close();
+  event.waitUntil(
+    clients.matchAll({ type: 'window', includeUncontrolled: true }).then(clientList => {
+      const url = event.notification.data.url;
+      for (const client of clientList) {
+        if (client.url.includes(url) && 'focus' in client) {
+          return client.focus();
+        }
+      }
+      if (clients.openWindow) {
+        return clients.openWindow(url);
+      }
+    })
+  );
+});
+
+// PWA: serve cached assets for offline support (minimal)
+self.addEventListener('fetch', event => {
+  // Pass-through — no offline caching in v1
+});