bug(self-hosting): Chrome extension login fails on self-hosted instances (missing CAP_CHROME_EXTENSION_ID)

[jerryno6]

Bug Description

When self-hosting Cap using the default Docker Compose templates (docker-compose.yml or docker-compose.coolify.yml), logging in via the Chrome extension fails with a 400 Bad Request or an HttpApiDecodeError indicating redirectUri validation issues.

Steps to Reproduce

1. Deploy Cap using the self-hosted Docker templates.
2. Configure the Chrome Extension's Cap URL to point to your self-hosted instance (e.g., https://cap.yourdomain.com).
3. Click "Log In" in the extension.
4. The extension attempts to authenticate against /api/extension/auth/start but receives a 400 Bad Request / failure.

  Could not reach Cap extension auth at https://cap.yourdomain.com. Start the local web server with pnpm dev:extension and make sure the extension Options Cap URL is
  https://cap.hapytek.com. Redirect URI: https://fefjaffcodfiogbbngmjkcjpbpclbdcp.chromiumapp.org/. 400

Technical Context

In packages/env/server.ts, the environment variable CAP_CHROME_EXTENSION_ID is used to validate the authorized Chrome extension ID. However:

• CAP_CHROME_EXTENSION_ID is not mapped to the container in docker-compose.yml or docker-compose.coolify.yml under the cap-web service.
• The parameter is undocumented and missing from the env template files (e.g., docker-compose.coolify.env.example), making it impossible for self-hosted instances to authorize Chrome extension logins out-of-the-box.

[linear]

CAP-753

[tembo]

The validation logic for this lives in packages/web-backend/src/Extension/Http.ts in the validateExtensionRedirectUri function. The key behavior is:

1. If CAP_CHROME_EXTENSION_ID is set, the redirect URI's extension ID must match exactly
2. If not set, extension auth is only allowed for localhost development (non-production + localhost/127.0.0.1 hostname)
3. Self-hosted deployments fail because they're neither localhost nor have the env var configured

The official Chrome Web Store extension ID is fefjaffcodfiogbbngmjkcjpbpclbdcp (visible in the store listing URL referenced in apps/web/lib/chrome-extension.ts).

For a workaround until this is merged, add to your cap-web service environment:

CAP_CHROME_EXTENSION_ID: fefjaffcodfiogbbngmjkcjpbpclbdcp

PR #1992 addresses this by adding the variable to the Docker Compose files and documenting it in the env example.