Add note context visibility in chat and standardize UI design tokens

Improve chat context: build_context() now returns metadata about auto-found
notes, emitted as an SSE event so the frontend can display context pills
showing which notes influenced the response. Users can promote notes for
deeper context (+) or exclude irrelevant ones (x). A note picker lets users
manually attach notes. Multi-word search uses per-term AND matching, and
auto-search iterates keywords individually for broader OR-style coverage.

Standardize styling: introduce CSS design tokens (--radius-sm/md/lg/pill,
--color-success/warning/overlay, --focus-ring) and migrate all components
to use them. Fix header alignment to full-width, add active nav link state,
replace hardcoded colors with CSS variables, and normalize button padding.

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

src/fabledassistant/services/chat.py

@@ -14,10 +14,13 @@ async def create_conversation(title: str = "", model: str = "") -> Conversation:
         conv = Conversation(title=title, model=model)
         session.add(conv)
         await session.commit()
-        await session.refresh(conv)
-        # Initialize empty messages list for to_dict()
-        conv.messages = []
-        return conv
+        # Re-fetch with messages eagerly loaded to avoid lazy-load in async context
+        result = await session.execute(
+            select(Conversation)
+            .options(selectinload(Conversation.messages))
+            .where(Conversation.id == conv.id)
+        )
+        return result.scalars().first()
 
 
 async def get_conversation(conversation_id: int) -> Conversation | None: