feat: add dev container for zero-config local development

.devcontainer/devcontainer.json

@@ -0,0 +1,31 @@
+{
+  "name": "Cal.diy",
+  "dockerComposeFile": "docker-compose.yml",
+  "service": "app",
+  "workspaceFolder": "/workspace",
+
+  // Override DATABASE_URL/REDIS_URL to use the Docker service names.
+  // These take precedence over .env, so no need to edit that file for the DB connection.
+  "remoteEnv": {
+    "DATABASE_URL": "postgresql://postgres:postgres@database:5432/calendso",
+    "DATABASE_DIRECT_URL": "postgresql://postgres:postgres@database:5432/calendso",
+    "REDIS_URL": "redis://redis:6379"
+  },
+
+  // On first container start: copy .env.example → .env only when .env is absent, then always install deps
+  // HUSKY=0 skips git hook installation, which fails in container environments
+  "postCreateCommand": "[ -f .env ] || cp .env.example .env; HUSKY=0 yarn install",
+
+  // Forward the web app port to the host
+  "forwardPorts": [3000],
+
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "biomejs.biome",
+        "bradlc.vscode-tailwindcss",
+        "prisma.prisma"
+      ]
+    }
+  }
+}

.devcontainer/docker-compose.yml

@@ -0,0 +1,34 @@
+# Dev container services - PostgreSQL and Redis for local development.
+# The app itself runs in the devcontainer, not here.
+services:
+  app:
+    image: mcr.microsoft.com/devcontainers/javascript-node:1-20-bookworm
+    volumes:
+      - ..:/workspace:cached
+    command: sleep infinity
+    depends_on:
+      - database
+      - redis
+
+  database:
+    image: postgres:15-alpine
+    restart: unless-stopped
+    environment:
+      POSTGRES_USER: postgres
+      POSTGRES_PASSWORD: postgres
+      POSTGRES_DB: calendso
+    ports:
+      # Expose on 5450 to match DATABASE_URL in .env.example
+      - "5450:5432"
+    volumes:
+      - postgres-data:/var/lib/postgresql/data
+
+  redis:
+    image: redis:7-alpine
+    restart: unless-stopped
+    volumes:
+      - redis-data:/data
+
+volumes:
+  postgres-data:
+  redis-data:

README.md

@@ -190,6 +190,46 @@ for Logger level to be set at info, for example.
 
 [![Open in Gitpod](https://gitpod.io/button/open-in-gitpod.svg)](https://gitpod.io/#https://github.com/calcom/cal.diy)
 
+#### Dev Container setup
+
+A Dev Container configuration is included so you can spin up a fully working development environment without installing PostgreSQL or Redis locally. It works with [VS Code Dev Containers](https://code.visualstudio.com/docs/devcontainers/containers) and [GitHub Codespaces](https://github.com/features/codespaces).
+
+**Requirements:** [Docker](https://www.docker.com/get-started) and the [VS Code Dev Containers extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers).
+
+1. Open the project in VS Code and click **Reopen in Container** when prompted (or run `Dev Containers: Reopen in Container` from the Command Palette).
+
+2. On first start, the container will automatically:
+   - Copy `.env.example` to `.env` (skipped if `.env` already exists)
+   - Run `yarn install`
+
+3. Open `.env` and fill in the two required secrets:
+
+   ```sh
+   # Generate NEXTAUTH_SECRET
+   openssl rand -base64 32
+
+   # Generate CALENDSO_ENCRYPTION_KEY (must be 32 bytes for AES256)
+   openssl rand -base64 24
+   ```
+
+   > The `DATABASE_URL` and `REDIS_URL` are pre-configured by the Dev Container and do not need to be changed.
+
+4. Run database migrations:
+
+   ```sh
+   yarn workspace @calcom/prisma db-migrate
+   ```
+
+5. Start the dev server:
+
+   ```sh
+   yarn dev
+   ```
+
+6. Open [http://localhost:3000](http://localhost:3000).
+
+> **Note:** PostgreSQL is exposed on host port `5450` and Redis on `6379`, matching the defaults in `.env.example`. This lets you connect to the database with tools like TablePlus or psql from your host machine without any extra configuration.
+
 #### Manual setup
 
 1. Configure environment variables in the `.env` file. Replace `<user>`, `<pass>`, `<db-host>`, and `<db-port>` with their applicable values