feat: add custom S3 endpoint support + Garage standalone storage

Add TRANSCRIPT_STORAGE_AWS_ENDPOINT_URL setting to enable S3-compatible
backends (Garage, MinIO). When set, uses path-style addressing and
routes all requests to the custom endpoint. When unset, AWS behavior
is unchanged.

- AwsStorage: accept aws_endpoint_url, pass to all 6 session.client()
  calls, configure path-style addressing and base_url
- Fix 4 direct AwsStorage constructions in Hatchet workflows to pass
  endpoint_url (would have silently targeted wrong endpoint)
- Standalone: add Garage service to docker-compose.standalone.yml,
  setup script initializes layout/bucket/key and writes credentials
- Fix compose_cmd() bug: Mac path was missing standalone yml
- garage.toml template with runtime secret generation via openssl

docker-compose.standalone.yml

@@ -6,6 +6,23 @@
 # On Mac: Ollama runs natively (Metal GPU) — no profile needed, services here unused.
 
 services:
+  garage:
+    image: dxflrs/garage:v1.1.0
+    ports:
+      - "3900:3900"   # S3 API
+      - "3903:3903"   # Admin API
+    volumes:
+      - garage_data:/var/lib/garage/data
+      - garage_meta:/var/lib/garage/meta
+      - ./data/garage.toml:/etc/garage.toml:ro
+    restart: unless-stopped
+    healthcheck:
+      test: ["CMD", "curl", "-sf", "http://localhost:3903/health"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+      start_period: 5s
+
   ollama:
     image: ollama/ollama:latest
     profiles: ["ollama-gpu"]
@@ -42,4 +59,6 @@ services:
       retries: 5
 
 volumes:
+  garage_data:
+  garage_meta:
   ollama_data: