fix: nahravanie velkych obrazkov - priamo do Supabase cez podpisanu URL, zmensenie na 2000 px

Vercel odmietal poziadavky nad 4,5 MB (Request Entity Too Large) a bucket
berie najviac 10 MB.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/api/upload/route.ts

@@ -1,42 +1,30 @@
 import { NextRequest, NextResponse } from 'next/server';
 import { getSupabaseAdmin } from '@/lib/supabase';
 
+const BUCKET = 'newsletter-assets';
+
+// Vydá podpísanú adresu na nahratie súboru priamo z prehliadača do Supabase Storage.
+// Samotný súbor cez server nejde – Vercel by odmietol požiadavky nad 4,5 MB („Request Entity Too Large“).
 export async function POST(req: NextRequest) {
   try {
-    const formData = await req.formData();
-    const file = formData.get('file') as File | null;
-
-    if (!file) {
-      return NextResponse.json({ error: 'Súbor nebol poskytnutý.' }, { status: 400 });
+    const { name } = (await req.json()) as { name?: string };
+    if (!name) {
+      return NextResponse.json({ error: 'Chýba názov súboru.' }, { status: 400 });
     }
 
     const admin = getSupabaseAdmin();
-    const safeName = file.name.replace(/[^a-zA-Z0-9._-]/g, '_');
+    const safeName = name.replace(/[^a-zA-Z0-9._-]/g, '_');
     const path = `uploads/${Date.now()}-${safeName}`;
 
-    const arrayBuffer = await file.arrayBuffer();
-    const buffer = Buffer.from(arrayBuffer);
-
-    const { error: uploadError } = await admin.storage
-      .from('newsletter-assets')
-      .upload(path, buffer, {
-        contentType: file.type || 'image/png',
-        upsert: true
-      });
-
-    if (uploadError) {
-      console.error('Upload to Supabase Storage error:', uploadError);
-      return NextResponse.json({ error: uploadError.message }, { status: 500 });
+    const { data, error } = await admin.storage.from(BUCKET).createSignedUploadUrl(path);
+    if (error || !data) {
+      console.error('Signed upload URL error:', error);
+      return NextResponse.json({ error: error?.message || 'Nepodarilo sa pripraviť nahratie' }, { status: 500 });
     }
 
-    const { data: pubData } = admin.storage
-      .from('newsletter-assets')
-      .getPublicUrl(path);
+    const { data: pubData } = admin.storage.from(BUCKET).getPublicUrl(path);
 
-    return NextResponse.json({
-      success: true,
-      url: pubData.publicUrl
-    });
+    return NextResponse.json({ success: true, path, token: data.token, url: pubData.publicUrl });
   } catch (err: any) {
     console.error('API /upload error:', err);
     return NextResponse.json({ error: err.message || 'Chyba servera pri nahrávaní súboru' }, { status: 500 });