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/api/routes/posts.py

@@ -220,6 +220,62 @@ async def reject_post(post_id: int, db: Session = Depends(get_db)):
     return {"message": "Post rechazado", "post_id": post_id}
 
 
+@router.post("/{post_id}/publish")
+async def publish_post_now(post_id: int, db: Session = Depends(get_db)):
+    """Publicar un post inmediatamente."""
+    from worker.tasks.publish_post import publish_to_platform
+
+    post = db.query(Post).filter(Post.id == post_id).first()
+    if not post:
+        raise HTTPException(status_code=404, detail="Post no encontrado")
+
+    if post.status not in ["draft", "pending_approval", "scheduled", "failed"]:
+        raise HTTPException(
+            status_code=400,
+            detail=f"No se puede publicar un post con status '{post.status}'"
+        )
+
+    # Cambiar estado a publishing
+    post.status = "publishing"
+    db.commit()
+
+    # Encolar tarea de publicación para cada plataforma
+    for platform in post.platforms:
+        publish_to_platform.delay(post.id, platform)
+
+    return {
+        "success": True,
+        "message": "Post enviado a publicación",
+        "post_id": post_id,
+        "platforms": post.platforms
+    }
+
+
+@router.post("/{post_id}/mark-published")
+async def mark_post_as_published(post_id: int, db: Session = Depends(get_db)):
+    """Marcar un post como publicado manualmente (sin usar API)."""
+    post = db.query(Post).filter(Post.id == post_id).first()
+    if not post:
+        raise HTTPException(status_code=404, detail="Post no encontrado")
+
+    if post.status not in ["draft", "pending_approval", "scheduled", "failed"]:
+        raise HTTPException(
+            status_code=400,
+            detail=f"No se puede marcar un post con status '{post.status}'"
+        )
+
+    post.status = "published"
+    post.published_at = datetime.utcnow()
+    post.error_message = None
+    db.commit()
+
+    return {
+        "success": True,
+        "message": "Post marcado como publicado",
+        "post_id": post_id
+    }
+
+
 @router.post("/{post_id}/regenerate")
 async def regenerate_post(post_id: int, db: Session = Depends(get_db)):
     """Regenerar contenido de un post con IA."""