chore: prepare production deploy with API hardening and Railway adapter

* Harden API routes with rate limits, upload cap, and edit dedupe.

Protect expensive endpoints from abuse, reject oversized mood uploads, dedupe concurrent edit-images calls, and surface Kakao search failures instead of silent mock fallback.

Co-authored-by: Cursor <cursoragent@cursor.com>

* chore: switch to adapter-node for Railway deploy

---------

Co-authored-by: Cursor <cursoragent@cursor.com>

svelte.config.js

@@ -1,4 +1,4 @@
-import adapter from '@sveltejs/adapter-auto';
+import adapter from '@sveltejs/adapter-node';
 
 /** @type {import('@sveltejs/kit').Config} */
 const config = {
@@ -7,9 +7,6 @@ const config = {
 		runes: ({ filename }) => (filename.split(/[/\\]/).includes('node_modules') ? undefined : true)
 	},
 	kit: {
-		// adapter-auto only supports some environments, see https://svelte.dev/docs/kit/adapter-auto for a list.
-		// If your environment is not supported, or you settled on a specific environment, switch out the adapter.
-		// See https://svelte.dev/docs/kit/adapters for more information about adapters.
 		adapter: adapter()
 	}
 };