Initialize devcontainer

.devcontainer/Dockerfile

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+ARG RUBY_VERSION=3.3.5
+FROM ghcr.io/rails/devcontainer/images/ruby:$RUBY_VERSION

.devcontainer/compose.yaml

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+name: "Audiences Dev"
+
+services:
+  dev:
+    build:
+      context: .
+      dockerfile: .devcontainer/Dockerfile
+
+    volumes:
+    - .:/workspaces:cached
+
+    # Overrides default command so things don't shut down after the process ends.
+    command: sleep infinity
+
+    # Uncomment the next line to use a non-root user for all processes.
+    # user: vscode
+
+    # Use "forwardPorts" in **devcontainer.json** to forward an app port locally.
+    # (Adding the "ports" property to this file will not forward from a Codespace.)
+    depends_on:
+    - dummy-web
+
+volumes:
+  redis-data:

.devcontainer/devcontainer.json

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+// For format details, see https://aka.ms/devcontainer.json. For config options, see the
+// README at: https://github.com/devcontainers/templates/tree/main/src/ruby
+{
+  "name": "audiences",
+  "dockerComposeFile": ["../docker-compose.yml", "compose.yaml"],
+  "service": "dev",
+  "workspaceFolder": "/workspaces",
+
+  // Features to add to the dev container. More info: https://containers.dev/features.
+  "features": {
+    "ghcr.io/devcontainers/features/github-cli:1": {},
+    "ghcr.io/rails/devcontainer/features/bundler-cache:1": {},
+    "ghcr.io/rails/devcontainer/features/mysql-client": {},
+    "ghcr.io/rails/devcontainer/features/postgres-client": {}
+  },
+
+  "containerEnv": {
+    "RAILS_ENV": "development",
+    "VITE_RUBY_HOST": "dummy-vite",
+    "DATABASE_HOST": "mysql"
+  },
+
+  // Use 'forwardPorts' to make a list of ports inside the container available locally.
+  "forwardPorts": [3000, 6379]
+
+  // Configure tool-specific properties.
+  // "customizations": {},
+
+  // Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.
+  // "remoteUser": "root",
+
+  // Use 'postCreateCommand' to run commands after the container is created.
+  // "postCreateCommand": "bin/setup"
+}