docs: add consolidated installation guide

Add docs/INSTALL.md with two installation paths:
- Option A: Docker Compose (all-in-one with PostgreSQL, MinIO,
  OpenLDAP, and optional nginx)
- Option B: Daemon install (systemd with external services, links to
  setup instructions for PostgreSQL, MinIO, FreeIPA, nginx)

Includes LDAP user/group management instructions, verification steps,
and upgrade procedures for both paths.

Update README.md Quick Start to point to INSTALL.md, add to docs table.
Add redirect banner to DEPLOYMENT.md for first-time users.
Add comments to docker-compose.prod.yaml noting unsupported env vars.

deployments/docker-compose.prod.yaml

@@ -16,22 +16,22 @@ services:
     restart: unless-stopped
     environment:
       # Database connection (psql.example.internal)
+      # Supported as direct env var overrides in the Go config loader:
       SILO_DB_HOST: psql.example.internal
-      SILO_DB_PORT: 5432
       SILO_DB_NAME: silo
       SILO_DB_USER: silo
       SILO_DB_PASSWORD: ${SILO_DB_PASSWORD:?Database password required}
-      SILO_DB_SSLMODE: require
+      # Note: SILO_DB_PORT and SILO_DB_SSLMODE are NOT supported as direct
+      # env var overrides. Set these in config.yaml instead, or use ${VAR}
+      # syntax in the YAML file. See docs/CONFIGURATION.md for details.
 
       # MinIO storage (minio.example.internal)
+      # Supported as direct env var overrides:
       SILO_MINIO_ENDPOINT: minio.example.internal:9000
       SILO_MINIO_ACCESS_KEY: ${SILO_MINIO_ACCESS_KEY:?MinIO access key required}
       SILO_MINIO_SECRET_KEY: ${SILO_MINIO_SECRET_KEY:?MinIO secret key required}
-      SILO_MINIO_BUCKET: silo-files
-      SILO_MINIO_USE_SSL: "true"
-
-      # Server settings
-      SILO_SERVER_BASE_URL: ${SILO_BASE_URL:-http://silo.example.internal:8080}
+      # Note: SILO_MINIO_BUCKET and SILO_MINIO_USE_SSL are NOT supported as
+      # direct env var overrides. Set these in config.yaml instead.
     ports:
       - "8080:8080"
     volumes: