fix: litestream healthcheck gate + 1yr retention

Re-enable deploy gate on litestream: pgrep-based healthcheck with 6
retries (30s window) after a 15s start period — broken backups now
fail the deploy loudly instead of silently succeeding.

Extend retention from 7d to 1yr (8760h): WAL frames are tiny for a
low-traffic app, R2 free tier covers years of storage.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.prod.yml

@@ -35,7 +35,11 @@ services:
       - app-data:/app/data
       - ./padelnomics/litestream.yml:/etc/litestream.yml:ro
     healthcheck:
-      disable: true
+      test: ["CMD-SHELL", "pgrep -x litestream > /dev/null"]
+      interval: 5s
+      timeout: 5s
+      retries: 6
+      start_period: 15s
 
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