Add settings page, model management, and chat UX improvements

- Settings infrastructure: key-value settings table, GET/PUT API, Pinia store
- Configurable assistant name (default "Fable") in settings and LLM system prompt
- Model catalog with 18 models in 3 categories (General Purpose, Coding,
  Uncensored / Creative Writing) with download/select/remove functionality
- Move Ollama status indicator from chat views to global nav bar
- Chat bubble layout: user messages right-aligned, assistant left-aligned
- Floating dark input bar with auto-focus and circular send button
- Fix HTML entity rendering (' apostrophe issue in marked/DOMPurify pipeline)
- Fix new chat button navigation (fetchConversation before router.push)
- Recent chats section on home page with "New Chat" button
- Update summary.md with Phase 4.5 changes

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

src/fabledassistant/models/__init__.py

@@ -13,3 +13,4 @@ class Base(DeclarativeBase):
 
 from fabledassistant.models.note import Note, TaskPriority, TaskStatus  # noqa: E402, F401
 from fabledassistant.models.conversation import Conversation, Message  # noqa: E402, F401
+from fabledassistant.models.setting import Setting  # noqa: E402, F401