feat(agent): add voice input and photo attachments to assistant

Wire mic through Whisper-compatible transcriptions on LLM_BASE_URL.

Photos upload to MinIO and reach the vision model as base64 image_url parts.

src/modules/agent/server/resolve-images.ts

@@ -0,0 +1,35 @@
+import { minioClient, MINIO_BUCKET } from "@/lib/minio";
+
+const UPLOAD_PATH_PREFIX = "/api/uploads/";
+
+function uploadKeyFromUrl(url: string): string | null {
+  if (!url.startsWith(UPLOAD_PATH_PREFIX)) return null;
+  const key = url.slice(UPLOAD_PATH_PREFIX.length);
+  if (!key || key.includes("..")) return null;
+  return key;
+}
+
+export async function resolveAssistantImageDataUrl(url: string): Promise<string> {
+  const key = uploadKeyFromUrl(url);
+  if (!key) {
+    throw new Error("Unsupported image URL");
+  }
+
+  const stream = await minioClient.getObject(MINIO_BUCKET, key);
+  const chunks: Buffer[] = [];
+  for await (const chunk of stream) {
+    chunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk as Uint8Array));
+  }
+  const buffer = Buffer.concat(chunks);
+
+  const stat = await minioClient.statObject(MINIO_BUCKET, key);
+  const metaData = stat.metaData as Record<string, string> | undefined;
+  const contentType =
+    metaData?.["content-type"] ?? metaData?.["Content-Type"] ?? "application/octet-stream";
+
+  return `data:${contentType};base64,${buffer.toString("base64")}`;
+}
+
+export async function resolveAssistantImageDataUrls(urls: string[]): Promise<string[]> {
+  return Promise.all(urls.map((url) => resolveAssistantImageDataUrl(url)));
+}