fix(auth): export MISSING_PASSWORD in AuthErrorCodes

[Navya-arugonda]

Summary
Export MISSING_PASSWORD: 'auth/missing-password' via AuthErrorCodes in @firebase/auth.

Why
The SDK can throw auth/missing-password, but it wasn’t exposed via AuthErrorCodes, forcing developers to hardcode the string.

Tests
Adds a Node unit test asserting:
AuthErrorCodes.MISSING_PASSWORD === 'auth/missing-password'.

Fixes
Fixes #9270

CLA
I have signed the Google Contributor License Agreement.

[changeset-bot]

🦋 Changeset detected

Latest commit: a032cd8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
@firebase/auth	Patch
firebase	Patch
@firebase/auth-compat	Patch

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[dlarocque]

When we make additions to public APIs, we have to update our reference documentation here on this website: https://firebase.google.com/docs/reference. The documentation hosted on that website is generated from the code in our SDK, and stored in the docs-devsite/ directory.

Since you made a public API addition, you need to generate the documentation for this new API. You can do this by running the yarn docgen:all script and committing the changes. The script will probably make changes to docs-devsite/auth.md in this case.

[Navya-arugonda]

Thanks for the review!
I’ve moved MISSING_PASSWORD below MISSING_PHONE_NUMBER, reverted the tsconfig.json changes, and removed the unnecessary test file.
Please let me know if any further adjustments are needed.

[Navya-arugonda]

Thanks for the reminder!
I’ve generated and committed the updated docs-devsite/auth.md to include the MISSING_PASSWORD export.