feat(29-01): extract dominant color in image upload endpoints

Both POST /api/images and POST /api/images/from-url now return
dominantColor in their response body.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/server/routes/images.ts

@@ -2,7 +2,10 @@ import { randomUUID } from "node:crypto";
 import { zValidator } from "@hono/zod-validator";
 import { Hono } from "hono";
 import { z } from "zod";
-import { fetchImageFromUrl } from "../services/image.service";
+import {
+	extractDominantColor,
+	fetchImageFromUrl,
+} from "../services/image.service";
 import { uploadImage } from "../services/storage.service";
 
 const ALLOWED_TYPES = ["image/jpeg", "image/png", "image/webp"];
@@ -59,7 +62,10 @@ app.post("/", async (c) => {
 	const buffer = await file.arrayBuffer();
 	await uploadImage(Buffer.from(buffer), filename, file.type);
 
-	return c.json({ filename }, 201);
+	// Extract dominant color for adaptive background fill
+	const dominantColor = await extractDominantColor(buffer);
+
+	return c.json({ filename, dominantColor }, 201);
 });
 
 export { app as imageRoutes };