Add invitation system, table of contents, actionable dashboard, and settings improvements

Invitation system (Phase 5.7):
- invitation_tokens table (migration 0012) with SHA256-hashed tokens, 7-day expiry
- Admin CRUD endpoints: POST/GET/DELETE /api/admin/invitations
- Branded invitation email with registration link
- /register-invite frontend view with token validation and account creation
- Admin UI: invite form + pending invitations table with revoke
- Configurable base URL setting for email links (replaces hardcoded Config.BASE_URL)

Table of contents + markdown improvements (Phase 5.8):
- TableOfContents component: sticky sidebar, heading parsing, smooth-scroll
- Custom marked renderer adds id attributes to headings for anchor links
- stripFirstLineTags() prevents leading #tags from rendering as headings
- NoteViewerView/TaskViewerView flex layout with TOC sidebar (hidden ≤1200px)
- Model catalog refresh: added llama3.2/3.3, gemma3, qwen3, phi4, deepseek-r1,
  qwen2.5-coder, dolphin3; added Reasoning category; removed discontinued models
- Settings model section split into Installed/Available tabs

Actionable dashboard (Phase 5.9):
- due_before/due_after query params on /api/tasks (exclusive < / inclusive >=)
- HomeView rewritten: overdue (red accent), due today, in progress, chats, notes
- 5 parallel API calls via Promise.allSettled
- Client-side done filtering and in-progress deduplication
- Task sections hidden when empty; status toggle removes done tasks

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

src/fabledassistant/services/notes.py

@@ -51,6 +51,8 @@ async def list_notes(
     is_task: bool | None = None,
     status: str | None = None,
     priority: str | None = None,
+    due_before: date | None = None,
+    due_after: date | None = None,
     sort: str = "updated_at",
     order: str = "desc",
     limit: int = 50,
@@ -96,6 +98,13 @@ async def list_notes(
             query = query.where(Note.priority == priority)
             count_query = count_query.where(Note.priority == priority)
 
+        if due_before is not None:
+            query = query.where(Note.due_date < due_before)
+            count_query = count_query.where(Note.due_date < due_before)
+        if due_after is not None:
+            query = query.where(Note.due_date >= due_after)
+            count_query = count_query.where(Note.due_date >= due_after)
+
         sort_col = getattr(Note, sort, Note.updated_at)
         if order == "asc":
             query = query.order_by(sort_col.asc())