Auto-upload stems to Gokapi on completion, save share link

- New helpers: parse_stems_urls, upload_to_gokapi, process_stems_to_gokapi
- Stems webhook handler now downloads stem files from MusicGPT CDN,
  zips them, uploads to Gokapi with 30-day expiry, saves the Gokapi
  download URL to stems_link in the DB
- Download Stems button uses stems_link (Gokapi URL) when available,
  falls back to the zip endpoint if not
- Config: GOKAPI_URL, GOKAPI_API_KEY, GOKAPI_EXPIRY_DAYS env vars
- docker-compose: GOKAPI_* environment variables added

app.py

@@ -66,6 +66,7 @@ from helpers import (
     musicgpt_generate_request, musicgpt_queue_stems, musicgpt_poll_status,
     download_musicgpt_outputs, format_musicgpt_cost, get_musicgpt_cost_totals,
     download_album_cover,
+    process_stems_to_gokapi,
     get_ntfy_config, send_ntfy,
     sign_prompt_callback, verify_prompt_callback, build_prompt_callback_url,
     send_email, build_signature_images,
@@ -419,7 +420,6 @@ def musicgpt_webhook():
             if not stems_url and audio_url_map:
                 stems_url = '; '.join(f"{k}: {v}" for k, v in audio_url_map.items())
             update_fields['stems_url'] = stems_url
-            update_fields['stems_link'] = stems_url
             try:
                 sc = float(data.get('conversion_cost') or 0)
             except (ValueError, TypeError):
@@ -429,6 +429,16 @@ def musicgpt_webhook():
         elif new_status in ('FAILED', 'ERROR'):
             update_fields['stems_error'] = data.get('reason') or data.get('error') or 'Extraction failed'
         update_request(req['id'], **update_fields)
+
+        # After stems are complete, upload them to Gokapi for a shareable link.
+        if new_status in ('COMPLETED', 'FINISHED') and Config.GOKAPI_URL and Config.GOKAPI_API_KEY:
+            row = db.execute('SELECT * FROM requests WHERE id = ?', (req['id'],)).fetchone()
+            req = dict(row)
+            gokapi_url, gokapi_err = process_stems_to_gokapi(req)
+            if gokapi_err:
+                app.logger.warning(f'Gokapi upload failed for request {req["id"]}: {gokapi_err}')
+            # Note: process_stems_to_gokapi already saves stems_link to the DB on success.
+
         return jsonify({'ok': True, 'request_id': req['id']}), 200
 
     return jsonify({'ok': False, 'reason': 'unknown_conversion_type'}), 400