debug: log POST body and full 400 response in compose

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

artifacts/postiz-mobile/app/(tabs)/compose.tsx

@@ -155,6 +155,7 @@ export default function ComposeScreen() {
         }),
       };
       const body = JSON.stringify(payload);
+      console.log("[compose] POST", `${baseUrl}/posts`, body);
 
       // eslint-disable-next-line no-undef
       const res = await globalThis.fetch(`${baseUrl}/posts`, {
@@ -170,7 +171,8 @@ export default function ComposeScreen() {
         let detail = "";
         try {
           const raw = await res.text();
-          detail = raw.slice(0, 300);
+          console.log("[compose] 400 body:", raw);
+          detail = raw.slice(0, 500);
         } catch {
           detail = res.statusText;
         }