fix(docker): relax healthcheck intervals and add start_period to postgres

The postgres container was being healthchecked every 5s which is
aggressive for a database, especially on slower machines or under load.
The bookhoard service was checked every 10s.

- Increase postgres healthcheck interval from 5s to 30s
- Add start_period: 10s to postgres to give it time to initialize
  before healthcheck failures count against retries
- Increase bookhoard healthcheck interval from 10s to 30s

docker-compose.yml

@@ -19,9 +19,10 @@ services:
       - "5432:5432"
     healthcheck:
       test: ["CMD-SHELL", "pg_isready -U postgres"]
-      interval: 5s
+      interval: 30s
       timeout: 5s
       retries: 3
+      start_period: 10s
     env_file:
       - .env
 
@@ -70,7 +71,7 @@ services:
       - bookhoard_conversion_cache:/app/cache/kepub
     healthcheck:
       test: ["CMD-SHELL", "curl -f http://localhost:8765/health || exit 1"]
-      interval: 10s
+      interval: 30s
       timeout: 5s
       retries: 3
       start_period: 10s