feat: Add publish and mark-published endpoints with validation

- Add /api/posts/{id}/publish endpoint for API-based publishing
- Add /api/posts/{id}/mark-published endpoint for manual workflow
- Add content length validation before publishing
- Update modal with "Ya lo publiqué" and "Publicar (API)" buttons
- Fix retry_count handling for None values

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/worker/tasks.py

@@ -60,10 +60,32 @@ def publish_post(self, post_id: int):
         for platform_name in post.platforms:
             try:
                 platform = Platform(platform_name)
+
+                # Get platform-specific content
+                platform_content = post.get_content_for_platform(platform_name)
+
+                # Pre-validate content length with descriptive error
+                publisher = publisher_manager.get_publisher(platform)
+                if publisher and hasattr(publisher, 'char_limit'):
+                    content_length = len(platform_content)
+                    if content_length > publisher.char_limit:
+                        error_msg = (
+                            f"Contenido excede límite: {content_length}/{publisher.char_limit} "
+                            f"caracteres (sobra {content_length - publisher.char_limit})"
+                        )
+                        logger.error(f"Validation failed for {platform_name}: {error_msg}")
+                        results[platform_name] = {
+                            "success": False,
+                            "post_id": None,
+                            "url": None,
+                            "error": error_msg
+                        }
+                        continue
+
                 result = run_async(
                     publisher_manager.publish(
                         platform=platform,
-                        content=post.content,
+                        content=platform_content,
                         image_path=post.image_url
                     )
                 )
@@ -90,10 +112,14 @@ def publish_post(self, post_id: int):
         if any_success:
             post.status = "published"
             post.published_at = datetime.utcnow()
-            post.publish_results = results
+            post.platform_post_ids = {
+                k: v.get("post_id") for k, v in results.items() if v.get("success")
+            }
         else:
             post.status = "failed"
-            post.publish_results = results
+            # Collect all error messages
+            errors = [f"{k}: {v.get('error')}" for k, v in results.items() if v.get("error")]
+            post.error_message = "\n".join(errors) if errors else "Unknown error"
 
         db.commit()