chore(compose): quote numeric env var values

Quote DATABASE_PORT and SERVER_PORT ("5432", "8765") in docker-compose.yml so they are treated as strings rather than YAML integers, avoiding type-coercion warnings from compose runtimes.

docker-compose.yml

@@ -35,14 +35,14 @@ services:
     environment:
       # Database Configuration
       DATABASE_HOST: db
-      DATABASE_PORT: 5432
+      DATABASE_PORT: "5432"
       DATABASE_USER: postgres
       DATABASE_PASSWORD: ${DBPASS}
       DATABASE_NAME: bookhoard
 
       # Application Configuration
       JWT_SECRET: ${JWT_SECRET}
-      SERVER_PORT: 8765
+      SERVER_PORT: "8765"
       # IMPORTANT: Device sync requires full URL with protocol
       # Local: http://localhost:8765
       # Local network: http://192.168.1.X:8765
@@ -86,7 +86,7 @@ services:
     environment:
       # Database Configuration
       DATABASE_HOST: db
-      DATABASE_PORT: 5432
+      DATABASE_PORT: "5432"
       DATABASE_USER: postgres
       DATABASE_PASSWORD: ${DBPASS}
       DATABASE_NAME: bookhoard
@@ -94,7 +94,7 @@ services:
 
       # Application Configuration
       JWT_SECRET: ${JWT_SECRET}
-      SERVER_PORT: 8765
+      SERVER_PORT: "8765"
 
       # Test Configuration
       TEST_MODE: "true"