fix(upload): bump middlewareClientMaxBodySize to 100mb

Next 16 caps any request body that flows through middleware at 10MB by
default. Our auth middleware matches every path, so /jobs/:id POSTs from
the file upload form hit 'Request body exceeded 10MB / Unexpected end of
form' the moment a user picked anything bigger than ~10MB total — the
server action never even ran.

serverActions.bodySizeLimit alone isn't enough; the new
middlewareClientMaxBodySize knob (Next 16) is the one that gates
middleware-handled bodies. Set both to 100mb so the 30MB-per-file bucket
limit is what actually matters.

The key isn't in NextConfig's TS types yet (Next 16.1), so it's assigned
via a narrow cast on the side rather than dropped into the object literal.

Also added console.log/error breadcrumbs to uploadJobFilesAction so the
next mystery upload failure shows up in the dev server log immediately
instead of silently bouncing back as 'Bağlantı hatası'.

next.config.ts

@@ -61,4 +61,10 @@ const nextConfig: NextConfig = {
   },
 };
 
+// Next 16 caps middleware-passed request bodies at 10MB by default. Our auth
+// middleware sees every request including job-file uploads — without this
+// override, multipart uploads larger than 10MB return "Unexpected end of
+// form". The key isn't in NextConfig's TS types yet (Next 16.1).
+(nextConfig as NextConfig & { middlewareClientMaxBodySize?: string }).middlewareClientMaxBodySize = "100mb";
+
 export default nextConfig;