executor abstraction, graphene to strawberry

docs/architecture/04-media-storage.md

@@ -68,6 +68,47 @@ aws s3 cp video.mp4 s3://mpr-media-in/
 aws s3 sync /local/media/ s3://mpr-media-in/
 ```
 
+## GCP Production (GCS via S3 compatibility)
+
+GCS exposes an S3-compatible API. The same `core/storage.py` boto3 code works
+with no changes — only the endpoint and credentials differ.
+
+### GCS HMAC Keys
+Generate under **Cloud Storage → Settings → Interoperability** in the GCP console.
+These act as `AWS_ACCESS_KEY_ID` / `AWS_SECRET_ACCESS_KEY`.
+
+### Configuration
+```bash
+S3_ENDPOINT_URL=https://storage.googleapis.com
+S3_BUCKET_IN=mpr-media-in
+S3_BUCKET_OUT=mpr-media-out
+AWS_ACCESS_KEY_ID=<GCS HMAC access key>
+AWS_SECRET_ACCESS_KEY=<GCS HMAC secret>
+
+# Executor
+MPR_EXECUTOR=gcp
+GCP_PROJECT_ID=my-project
+GCP_REGION=us-central1
+CLOUD_RUN_JOB=mpr-transcode
+CALLBACK_URL=https://mpr.mcrn.ar/api
+CALLBACK_API_KEY=<secret>
+```
+
+### Upload Files to GCS
+```bash
+gcloud storage cp video.mp4 gs://mpr-media-in/
+
+# Or with the aws CLI via compat endpoint
+aws --endpoint-url https://storage.googleapis.com s3 cp video.mp4 s3://mpr-media-in/
+```
+
+### Cloud Run Job Handler
+`task/gcp_handler.py` is the Cloud Run Job entrypoint. It reads the job payload
+from `MPR_JOB_PAYLOAD` (injected by `GCPExecutor`), uses `core/storage` for all
+GCS access (S3 compat), and POSTs the completion callback to the API.
+
+Set the Cloud Run Job command to: `python -m task.gcp_handler`
+
 ## Storage Module
 
 `core/storage.py` provides all S3 operations:
@@ -114,7 +155,14 @@ mutation { scanMediaFolder { found registered skipped files } }
 4. Uploads result to `S3_BUCKET_OUT`
 5. Calls back to API with result
 
-Both paths use the same S3 buckets and key structure.
+### Cloud Run Job Mode (GCP)
+1. `GCPExecutor` triggers Cloud Run Job with payload in `MPR_JOB_PAYLOAD`
+2. `task/gcp_handler.py` downloads source from `S3_BUCKET_IN` (GCS S3 compat)
+3. Runs FFmpeg in container
+4. Uploads result to `S3_BUCKET_OUT` (GCS S3 compat)
+5. Calls back to API with result
+
+All three paths use the same S3-compatible bucket names and key structure.
 
 ## Supported File Types