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>

src/fabledassistant/services/generation_task.py

@@ -147,6 +147,7 @@ async def run_generation(
     user_content: str,
     context_note_id: int | None = None,
     include_note_ids: list[int] | None = None,
+    excluded_note_ids: list[int] | None = None,
     think: bool = False,
 ) -> None:
     """Stream LLM response into buffer with periodic DB flushes."""
@@ -166,7 +167,7 @@ async def run_generation(
     # Phase 2: Summarize long conversation history if needed.
     history_to_use = history
     history_summary: str | None = None
-    if len(history) > 20:  # matches _HISTORY_SUMMARY_THRESHOLD in llm.py
+    if len(history) > 30:  # matches _HISTORY_SUMMARY_THRESHOLD in llm.py
         buf.append_event("status", {"status": "Summarizing conversation history..."})
         history_to_use, history_summary = await summarize_history_for_context(history, model)
 
@@ -177,6 +178,7 @@ async def run_generation(
         user_id, history_to_use, context_note_id, user_content,
         history_summary=history_summary,
         include_note_ids=include_note_ids,
+        excluded_note_ids=excluded_note_ids,
     ))
 
     messages, context_meta = await context_task
@@ -348,6 +350,22 @@ async def run_generation(
         buf.finished_at = time.monotonic()
         buf.append_event("done", {"done": True, "message_id": msg_id, "timing": timing})
 
+        # Fire push notification when complete (non-critical, fire-and-forget)
+        try:
+            from fabledassistant.services.push import send_push_notification, vapid_enabled
+            if vapid_enabled():
+                preview = buf.content_so_far[:120].rstrip()
+                if len(buf.content_so_far) > 120:
+                    preview += "…"
+                asyncio.create_task(send_push_notification(
+                    user_id,
+                    title="Response ready",
+                    body=preview,
+                    url=f"/chat/{conv_id}",
+                ))
+        except Exception:
+            logger.debug("Failed to schedule push notification", exc_info=True)
+
         # Title generation is non-critical — fire-and-forget so done fires immediately
         non_system = [m for m in messages if m["role"] != "system"]
         msg_count = len(non_system)