Add Ollama health check status indicator to chat views

Adds visibility into whether Ollama is reachable and the configured model
is ready before allowing chat. Prevents silent failures when the model is
still downloading or Ollama is unavailable.

- Backend: GET /api/chat/status endpoint checks Ollama /api/tags (5s timeout)
  Returns ollama availability + model readiness + default model name
- Frontend: OllamaStatus type, chat store polling (30s interval)
- ChatView: status dot + label in header (green/yellow/red), disabled send
- ChatPanel: compact status indicator in panel header, disabled send
- summary.md: updated with new endpoint, store changes, and component descriptions

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

frontend/src/types/chat.ts

@@ -24,3 +24,9 @@ export interface OllamaModel {
   name: string;
   size: number;
 }
+
+export interface OllamaStatus {
+  ollama: "available" | "unavailable";
+  model: "ready" | "not_found";
+  default_model: string;
+}