feat(ollama): add availability check before model operations

Add `ensureOllamaAvailable` function to lib/ollama.ts for checking and waiting for Ollama server health with configurable timeout.

Integrate the check in GET /api/ollama/models route with 3s timeout to prevent UI blocking, and in POST /api/ollama/pull route with 20s timeout to ensure availability before pulling models.

Update ChatContainer to always render ModelDropdown for better UX when no model is selected.

app/api/ollama/models/route.ts

@@ -1,5 +1,5 @@
 import { NextResponse } from "next/server";
-import { listModelsViaSdk, listModelsViaHttp } from "@/lib/ollama";
+import { listModelsViaSdk, listModelsViaHttp, ensureOllamaAvailable } from "@/lib/ollama";
 import {
   estimateCpuVram,
   inferDevice,
@@ -31,6 +31,8 @@ function normalizeModel(model: any): ModelInfo {
 export async function GET() {
   try {
     let models: any[] = [];
+    // Tentar garantir disponibilidade rapidamente (não bloquear longamente a UI)
+    await ensureOllamaAvailable({ timeoutMs: 3000 }).catch(() => {});
     try {
       models = await listModelsViaSdk();
     } catch {