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/services/settings.py

@@ -0,0 +1,28 @@
+from sqlalchemy import select
+
+from fabledassistant.models import async_session
+from fabledassistant.models.setting import Setting
+
+
+async def get_setting(key: str, default: str = "") -> str:
+    async with async_session() as session:
+        result = await session.execute(select(Setting).where(Setting.key == key))
+        setting = result.scalar_one_or_none()
+        return setting.value if setting else default
+
+
+async def set_setting(key: str, value: str) -> None:
+    async with async_session() as session:
+        result = await session.execute(select(Setting).where(Setting.key == key))
+        setting = result.scalar_one_or_none()
+        if setting:
+            setting.value = value
+        else:
+            session.add(Setting(key=key, value=value))
+        await session.commit()
+
+
+async def get_all_settings() -> dict[str, str]:
+    async with async_session() as session:
+        result = await session.execute(select(Setting))
+        return {s.key: s.value for s in result.scalars().all()}