Reduce Hypercorn workers to 1 per app to save ~600MB RAM

Each app was running 2 workers (~100MB each). On a 3.8GB system with
6 apps, the 12 workers consumed ~1.2GB and caused swap pressure.

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

docker-compose.yml

@@ -62,6 +62,7 @@ services:
       DATABASE_HOST: db
       DATABASE_PORT: "5432"
       RUN_MIGRATIONS: "true"
+      WORKERS: "1"
 
   market:
     <<: *app-common
@@ -78,6 +79,7 @@ services:
       REDIS_URL: redis://redis:6379/1
       DATABASE_HOST: db
       DATABASE_PORT: "5432"
+      WORKERS: "1"
 
   cart:
     <<: *app-common
@@ -91,6 +93,7 @@ services:
       REDIS_URL: redis://redis:6379/2
       DATABASE_HOST: db
       DATABASE_PORT: "5432"
+      WORKERS: "1"
 
   events:
     <<: *app-common
@@ -104,6 +107,7 @@ services:
       REDIS_URL: redis://redis:6379/3
       DATABASE_HOST: db
       DATABASE_PORT: "5432"
+      WORKERS: "1"
 
   federation:
     <<: *app-common
@@ -117,6 +121,7 @@ services:
       REDIS_URL: redis://redis:6379/4
       DATABASE_HOST: db
       DATABASE_PORT: "5432"
+      WORKERS: "1"
 
   account:
     <<: *app-common
@@ -130,6 +135,7 @@ services:
       REDIS_URL: redis://redis:6379/5
       DATABASE_HOST: db
       DATABASE_PORT: "5432"
+      WORKERS: "1"
 
   db:
     image: postgres:16