docs(auth): add email link authentication guide

[rutvik24]

Summary

• Add Auth email-link authentication guide and wire it into the docs nav.
• Cross-link related Auth docs (usage, phone, OIDC) and update the spellcheck dictionary.

Test plan

• yarn lint:markdown
• yarn lint:spellcheck
• Confirm Documentation / Spelling & Grammar check is green on the PR

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.40%. Comparing base (b7c4749) to head (238d9f4).
⚠️ Report is 20 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #9170      +/-   ##
============================================
+ Coverage     68.10%   68.40%   +0.31%     
- Complexity     1912     1915       +3     
============================================
  Files           510      516       +6     
  Lines         37877    37853      -24     
  Branches       5193     5183      -10     
============================================
+ Hits          25792    25890      +98     
+ Misses        10261    10178      -83     
+ Partials       1824     1785      -39     

Flag	Coverage Δ
android-native	63.76% <ø> (+0.03%)	⬆️
e2e-ts-android	54.15% <ø> (+0.17%)	⬆️
e2e-ts-ios	53.51% <ø> (-3.01%)	⬇️
e2e-ts-macos	49.67% <ø> (-0.06%)	⬇️
ios-native	68.79% <ø> (+0.16%)	⬆️
ios-ruby	100.00% <ø> (ø)
jest	45.48% <ø> (+0.44%)	⬆️

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[mikehardy]

Thank you for this - it's a substantial, carefully researched guide on a genuinely hard flow, and filling this gap in the RNFB docs is really appreciated.

Requesting a structural pass so the page matches the style of the upstream Firebase email-link docs: official default / non-branded path first (the way people will first integrate), then optional custom-domain / branded hosting. Community tools can be mentioned where they help, but please don't promote specific projects - same approach as our other auth pages (phone, social), which link official Firebase docs and leave third-party helpers as optional asides.

Inline comments have suggested copy where that might reduce back-and-forth. None of this is a knock on the work you've already done; it's aligning the page with how we document the rest of Auth and I think this will help a lot of people in one of the more difficult areas of cross-platform mobile dev

[rutvik24]

@mikehardy made some changes in the docs pls have a look if need any further changes do let me know

[mikehardy]

Hey @rutvik24 👋

Thanks for the update — this is much closer to how we document the rest of Auth. Default Hosting path first, migration off Dynamic Links, Expo, troubleshooting, the two-domain split: all the structural bits from the review landed.

One small tweak before merge: the intro to Optional community helpers. I want to acknowledge why people reach for community tools (branding in the email link, branded continue pages, custom domains) and that the work behind them may genuinely help — while making it crystal clear we don't control or endorse third-party repos and can't vouch for them.

Suggested replacement for that section intro:

The default Hosting path above is the simplest integration for most apps. The projects below were built by community contributors for setups that need more than that — a custom domain, your brand in the sign-in email (instead of the default firebaseapp.com link), a branded continue page, or association files on a host you already operate. That work may genuinely help when you have those requirements.

React Native Firebase does not maintain, control, or endorse these tools; we cannot vouch for their security or long-term availability. Prefer the default Hosting path when it fits, and evaluate each project for your own requirements.

And for the association-files forward reference (line ~88):

Community generators exist for these JSON files; they are optional and unofficial — see Optional community helpers at the end of this page.

Happy to approve once that's in. Cheers

[rutvik24]

@mikehardy updated the Optional community helpers intro with your suggested disclaimer (no maintain/control/endorse; cannot vouch for security or availability), and the association-files forward reference now says those generators are optional and unofficial.

Also reframed the two helpers:

• No existing website → ready-made hosting helper (email-link-host)
• Existing website → form-based file generator (App Universal Links Helper)

Happy to tweak further if anything still feels off.