feat: Docker Compose files in repos

compose.yaml, docker-compose.yml and their variants tracked by git are
listed under Repos, their services' environment variables as secrets,
named service.VAR.

- environment as a map or a list, and <<: *anchors shared between
  services; the secret patterns pick the keys, the rest hidden, with
  compose.secretPatterns for compose files' own.
- ${VAR}, $VAR, ${VAR:?…} and variables without a value are marked as
  references; docker-compose.example.yml and the like are hidden.
- Jasypt values decrypt with the service's JASYPT_ENCRYPTOR_PASSWORD.
- A blue Docker icon, themeable with composeColor.

docs/config.md

@@ -75,6 +75,7 @@ theme:
   databricksColor: ["#ff757f"]
   repoColor: ["#c099ff"]
   springColor: ["#c3e88d"]               # Spring Boot config files
+  composeColor: ["#82aaff"]              # Docker Compose files
 ```
 
 A role lazysecrets doesn't know, a typo or one from a newer version, is