feat: image generation integrated into content creation flow

Backend:
- When content_types includes "image", generate image via configured
  image provider (DALL-E, Replicate) after text generation
- Image prompt built from character niche + topic + visual style
- Graceful fallback: if image generation fails, post is text-only
- Post content_type set to "text+image" when image is attached

Frontend:
- ContentPage preview shows generated image above text when present
- Image displayed with full width and border

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/routers/content.py

@@ -171,12 +171,35 @@ def generate_content(
                 text, affiliate_link_dicts, character.topics or []
             )
 
+        # Generate image if requested
+        image_url = None
+        content_types = request.content_types if request.content_types else [request.content_type]
+        if "image" in content_types:
+            img_provider_name = _get_setting(db, "image_provider", current_user.id)
+            img_api_key = _get_setting(db, "image_api_key", current_user.id)
+            if img_provider_name and img_api_key:
+                try:
+                    img_provider = get_image_provider(img_provider_name, img_api_key)
+                    visual_style = character.visual_style or {}
+                    style_desc = visual_style.get("description", "")
+                    img_prompt = (
+                        f"Social media image for a {character.niche} content creator. "
+                        f"Topic: {request.topic_hint or text[:100]}. "
+                        f"Style: {style_desc} professional, clean, engaging.".strip()
+                    )
+                    image_url = img_provider.generate(img_prompt, size="1024x1024")
+                except Exception:
+                    pass  # Image generation failed, continue with text only
+
+        effective_type = "text+image" if image_url else "text"
+
         post = Post(
             batch_id=batch_id,
             character_id=character.id,
             user_id=current_user.id,
-            content_type=request.content_type,
+            content_type=effective_type,
             text_content=text,
+            image_url=image_url,
             hashtags=hashtags,
             affiliate_links_used=affiliate_links_used,
             llm_provider=provider_name,