feat(self-hosting): allow configuring CAP_CHROME_EXTENSION_ID for extension login

[jerryno6]

Problem

When deploying Cap on a self-hosted instance, attempting to log in via the Chrome extension results in a 400 Bad Request / authentication failure. This is because the Next.js backend checks the incoming redirectUri against the allowed Chrome Web Store extension ID (via the CAP_CHROME_EXTENSION_ID environment variable). Since this variable is not mapped to the container in the default Docker Compose configurations and is undocumented, extension logins fail on all self-hosted deployments.

Solution

1. Added the CAP_CHROME_EXTENSION_ID environment variable mapping to docker-compose.yml and docker-compose.coolify.yml under the cap-web service.
2. Added the optional parameter to docker-compose.coolify.env.example.
3. Documented the configuration parameter in README.md under the Self-Hosting environment list.

Fixes #1993

[greptile-apps]

Published Extension ID Misleads Self-Hosts

When an operator builds or loads their own extension, Chrome uses that extension's assigned ID in chrome.identity.getRedirectURL(), not the published Cap Web Store ID shown here. Following this snippet with a self-built extension makes the backend compare against the wrong ID and reject extension login with 400.

Suggested change

	CAP_CHROME_EXTENSION_ID=fefjaffcodfiogbbngmjkcjpbpclbdcp # Chrome Web Store extension ID allowed to receive auth keys
	CAP_CHROME_EXTENSION_ID=your-chrome-extension-id # Extension ID allowed to receive auth keys (e.g. fefjaffcodfiogbbngmjkcjpbpclbdcp for the published Chrome Web Store extension)

Context Used: CLAUDE.md (source)

Prompt To Fix With AI

This is a comment left during a code review.
Path: README.md
Line: 109

Comment:
**Published Extension ID Misleads Self-Hosts**

When an operator builds or loads their own extension, Chrome uses that extension's assigned ID in `chrome.identity.getRedirectURL()`, not the published Cap Web Store ID shown here. Following this snippet with a self-built extension makes the backend compare against the wrong ID and reject extension login with 400.

```suggestion
CAP_CHROME_EXTENSION_ID=your-chrome-extension-id # Extension ID allowed to receive auth keys (e.g. fefjaffcodfiogbbngmjkcjpbpclbdcp for the published Chrome Web Store extension)
```

**Context Used:** CLAUDE.md ([source](https://app.greptile.com/cap/github/capsoftware/cap/-/custom-context?memory=9a906542-f1fe-42c1-89a2-9f252d96d9f0))

How can I resolve this? If you propose a fix, please make it concise.

[tembo]

Hard-coding the published Web Store ID here might confuse self-hosters who build/load the extension themselves (their extension ID will differ). Might be clearer to show a placeholder and mention the published ID in a comment.

Suggested change

	CAP_CHROME_EXTENSION_ID=fefjaffcodfiogbbngmjkcjpbpclbdcp
	```
	# Chrome extension ID allowed to receive auth keys
	# Published Chrome Web Store extension: fefjaffcodfiogbbngmjkcjpbpclbdcp
	CAP_CHROME_EXTENSION_ID=your-chrome-extension-id

[jerryno6]

THis is the official chrome extension of CAP, we should keep it as it is. Just mention it in the comment is enough