chore: add CHARON_ENCRYPTION_KEY to all Docker Compose files and README

- Add encryption key environment variable to docker-compose.yml,
  docker-compose.dev.yml, docker-compose.local.yml, docker-compose.test.yml
- Update README.md Quick Start examples (compose and docker run)
- Include generation instructions: openssl rand -base64 32

Required for DNS provider and plugin features which encrypt sensitive data at rest.

.vscode/tasks.json

@@ -4,14 +4,14 @@
         {
             "label": "Build & Run: Local Docker Image",
             "type": "shell",
-            "command": "docker build -t charon:local . && docker compose -f docker-compose.test.yml up -d && echo 'Charon running at http://localhost:8080'",
+            "command": "docker build -t charon:local . && docker compose -f /projects/Charon/.docker/compose/docker-compose.test.yml up -d && echo 'Charon running at http://localhost:8080'",
             "group": "build",
             "problemMatcher": []
         },
         {
             "label": "Build & Run: Local Docker Image No-Cache",
             "type": "shell",
-            "command": "docker build --no-cache -t charon:local . && docker compose -f docker-compose.test.yml up -d && echo 'Charon running at http://localhost:8080'",
+            "command": "docker build --no-cache -t charon:local . && docker compose -f /projects/Charon/.docker/compose//projects/Charon/.docker/compose/docker-compose.test.yml up -d && echo 'Charon running at http://localhost:8080'",
             "group": "build",
             "problemMatcher": []
         },