chore: add .env.example and wire compose.yml to env vars

- .env.example documents all env vars with defaults (postgres creds, DATABASE_URL, TTLs, pool sizes)
- compose.yml reads postgres credentials and app config from .env via env_file
- .gitignore: track .env.example, ignore .env

compose.yml

@@ -3,13 +3,13 @@ services:
     image: postgres:16-alpine
     restart: unless-stopped
     environment:
-      POSTGRES_DB: goyomi
-      POSTGRES_USER: goyomi
-      POSTGRES_PASSWORD: goyomi
+      POSTGRES_DB: ${POSTGRES_DB}
+      POSTGRES_USER: ${POSTGRES_USER}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
     volumes:
       - postgres_data:/var/lib/postgresql/data
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U goyomi -d goyomi"]
+      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER} -d ${POSTGRES_DB}"]
       interval: 5s
       timeout: 5s
       retries: 10
@@ -25,11 +25,9 @@ services:
   app:
     build: .
     restart: unless-stopped
+    env_file: .env
     ports:
-      - "8080:8080"
-    environment:
-      DATABASE_URL: postgres://goyomi:goyomi@postgres:5432/goyomi?sslmode=disable
-      FLARESOLVERR_URL: http://flaresolverr:8191
+      - "${ADDR:-8080}:8080"
     depends_on:
       postgres:
         condition: service_healthy