ci: build images on every change, add install script

- docker job: buildx + GHA cache, GHCR push on main/tags via
  metadata-action tags, Trivy scan (report-only)
- fix: tag pushes now trigger the workflow so releases publish images
- root compose: parameterized host ports, backend healthcheck,
  frontend waits for healthy backend
- install.sh: generates .env secrets, builds, boots, waits for health
- README: easy-install section, port remap docs, CI badge

Authored By: TDvorak <[email protected]>

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

.env.example

@@ -5,6 +5,12 @@ DOMAIN=localhost
 ACME_EMAIL=admin@localhost
 ENVIRONMENT=development
 
+# Published host ports (change if they collide with other services)
+HTTP_PORT=3000
+API_PORT=8082
+POSTGRES_PORT=5432
+REDIS_PORT=6379
+
 # Database Configuration
 POSTGRES_DB=containr
 POSTGRES_USER=containr_user