Switch compose from env_file to environment blocks

Replace env_file: .env with explicit environment: variables using
${VAR} substitution. Works with both .env files (local dev) and
Portainer's environment UI (no .env file needed on the host).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose.yaml

@@ -2,7 +2,10 @@ services:
   db:
     image: postgres:16-alpine
     restart: unless-stopped
-    env_file: .env
+    environment:
+      - POSTGRES_USER=${POSTGRES_USER}
+      - POSTGRES_PASSWORD=${POSTGRES_PASSWORD}
+      - POSTGRES_DB=${POSTGRES_DB}
     volumes:
       - postgres_data:/var/lib/postgresql/data
     networks:
@@ -22,7 +25,15 @@ services:
     image: git.sentinelforest.xyz/rohskiddo/umbra-backend:main-latest
     build: ./backend
     restart: unless-stopped
-    env_file: .env
+    environment:
+      - DATABASE_URL=postgresql+asyncpg://${POSTGRES_USER}:${POSTGRES_PASSWORD}@db:5432/${POSTGRES_DB}
+      - SECRET_KEY=${SECRET_KEY}
+      - ENVIRONMENT=${ENVIRONMENT:-production}
+      - UMBRA_URL=${UMBRA_URL:-https://umbra.ghost6.xyz}
+      - OPENWEATHERMAP_API_KEY=${OPENWEATHERMAP_API_KEY:-}
+      - WEBAUTHN_RP_ID=${WEBAUTHN_RP_ID:-umbra.ghost6.xyz}
+      - WEBAUTHN_RP_NAME=${WEBAUTHN_RP_NAME:-UMBRA}
+      - WEBAUTHN_ORIGIN=${WEBAUTHN_ORIGIN:-https://umbra.ghost6.xyz}
     depends_on:
       db:
         condition: service_healthy