Use plugin-specific i18n domain for translations

[dereuromark]

Summary

• Convert the 2 __() calls in the unauthorized-handler middleware to __d('tinyauth', ...) so plugin strings live in their own domain.
• Add resources/locales/tinyauth.pot (1 unique msgid — the unauthorized-access fallback message) generated via bin/cake i18n extract so language packs can be derived from a stable POT.

Why

Plugin strings were landing in the host app's default domain. Anyone translating the host app would have ended up translating this plugin's UI under their own domain — and shipping a translated language pack with the plugin was effectively impossible.

Verification (local)

• phpunit: 111 / 111 (2 pre-existing deprecations, 11 pre-existing notices — unrelated to this change)
• phpstan: no errors
• phpcs: clean

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.59%. Comparing base (919f2d9) to head (79650da).

Files with missing lines	Patch %	Lines
...authorizedHandler/ForbiddenCakeRedirectHandler.php	0.00%	1 Missing ⚠️
...e/UnauthorizedHandler/ForbiddenRedirectHandler.php	0.00%	1 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff            @@
##             master     #166   +/-   ##
=========================================
  Coverage     67.59%   67.59%           
  Complexity      627      627           
=========================================
  Files            29       29           
  Lines          1614     1614           
=========================================
  Hits           1091     1091           
  Misses          523      523           

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