fix(GRO-867): proxy logo download through API server — eliminate mixed content

All logo S3 interactions are now server-proxied:
- GET /api/admin/settings/logo streams image bytes directly instead of
  returning a presigned S3 URL to the browser
- Upload already went through POST /api/admin/settings/logo/upload
- Frontend uses relative /api/admin/settings/logo path as img src,
  never a raw S3 URL
- Appends cache-buster query param (?t=Date.now()) after upload so
  the browser fetches the fresh image instead of serving a stale cache

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/lib/s3.ts

@@ -68,6 +68,20 @@ export async function deleteObject(key: string): Promise<void> {
   );
 }
 
+/** Read an object from S3 and return its body buffer and content type. */
+export async function getObject(key: string): Promise<{ body: Buffer; contentType: string }> {
+  const client = getS3Client();
+  const response = await client.send(
+    new GetObjectCommand({
+      Bucket: getBucket(),
+      Key: key,
+    })
+  );
+  const body = await response.Body!.transformToBuffer();
+  const contentType = response.ContentType ?? "application/octet-stream";
+  return { body, contentType };
+}
+
 /** Upload an object directly to S3 (server-side only, not a pre-signed URL). */
 export async function putObject(
   key: string,

apps/api/src/routes/settings.ts

@@ -2,7 +2,7 @@ import { Hono } from "hono";
 import { zValidator } from "@hono/zod-validator";
 import { z } from "zod/v3";
 import { eq, getDb, businessSettings } from "@groombook/db";
-import { getPresignedUploadUrl, getPresignedGetUrl, deleteObject, putObject } from "../lib/s3.js";
+import { getPresignedUploadUrl, getPresignedGetUrl, deleteObject, putObject, getObject } from "../lib/s3.js";
 import { requireSuperUser } from "../middleware/rbac.js";
 
 export const settingsRouter = new Hono();
@@ -215,7 +215,8 @@ settingsRouter.post(
 
 /**
  * GET /api/admin/settings/logo
- * Returns a presigned GET URL for the logo.
+ * Proxies the logo from S3 so the browser never sees an S3 URL.
+ * Returns the image bytes with proper Content-Type.
  */
 settingsRouter.get("/logo", async (c) => {
   const db = getDb();
@@ -224,8 +225,10 @@ settingsRouter.get("/logo", async (c) => {
   if (!row) return c.json({ error: "Settings not found" }, 404);
   if (!row.logoKey) return c.json({ error: "No logo on file" }, 404);
 
-  const url = await getPresignedGetUrl(row.logoKey);
-  return c.json({ url, logoKey: row.logoKey });
+  const { body, contentType } = await getObject(row.logoKey);
+  c.header("Content-Type", contentType);
+  c.header("Cache-Control", "public, max-age=86400");
+  return c.body(body);
 });
 
 /**