feat: add login command

[bhdnb]

Authorize without generating a config: crowdin login runs the same browser OAuth flow as init and saves the token to ~/.crowdin.yml, so agentic workflows can log in once and let every later command pick the credentials up from the identity file. -T stores an existing token without opening a browser; --base-url (or the domain in the browser token) is persisted alongside it for Enterprise.

The browser flow moves out of init/browserAuthServer.ts into utils/browserAuth.ts, which now also owns the open-and-wait driver both commands share, and init's token write becomes saveCredentials() in lib/identityFiles.ts.

Text output leaves the result line to the authorization spinner and the outro; json/toon/plain get the record.

Also isolate HOME in the exit-code integration tests: they spawn the CLI with no config, so a developer's own ~/.crowdin.yml made the "missing config" cases exit 2 instead of 102.

Documentation updated as well.

[codecov]

Codecov Report

❌ Patch coverage is 81.63265% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.69%. Comparing base (c0a4f40) to head (3f90d6e).

Files with missing lines	Patch %	Lines
src-next/cli/commands/login/LoginCommand.ts	69.10%	17 Missing ⚠️
src-next/cli/commands/init/InitCommand.ts	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1094      +/-   ##
==========================================
+ Coverage   92.20%   92.69%   +0.49%     
==========================================
  Files         141      143       +2     
  Lines       11485    11536      +51     
==========================================
+ Hits        10589    10692     +103     
+ Misses        896      844      -52     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.