Chore: Improve canonical email test for proton case insensitive mails

[Meldiron]

No description provided.

[greptile-apps]

Greptile Summary

This PR adds test cases to cover case-insensitive canonicalisation of ProtonMail addresses, specifically verifying that mixed- and upper-case local parts are lowercased and that proton.me / pm.me aliases are normalised to protonmail.com.

• ProtonmailTest.php: Three new direct-provider tests (mixed, upper, lower) correctly verify that getCanonical() lowercases the local part regardless of input casing.
• EmailTest.php: A baseline proton.me case is added to the regular block, and three case-variant entries are added to the case-insensitive block; the third entry in the case-insensitive group is all-lowercase and duplicates the regular-block entry rather than following the lowercase-local + mixed-domain pattern used by every other provider.

Confidence Score: 4/5

Safe to merge; all changes are test-only additions with no production code impact.

The only change is in test files, and the tests themselves are correct — they accurately describe the expected behaviour. The one inconsistency (the third case-insensitive entry being all-lowercase instead of following the mixed-domain pattern) is cosmetic and doesn't risk a false-positive or false-negative test result.

tests/EmailTest.php — the third entry in the new proton.me case-insensitive group.

Important Files Changed

Filename	Overview
tests/Canonicals/Providers/ProtonmailTest.php	Adds three case-sensitivity test cases (mixed, upper, lower) for the local part of a proton.me address; changes are correct and consistent with the existing test structure.
tests/EmailTest.php	Adds proton.me case-insensitive test cases in two sections; the third entry in the case-insensitive block is all-lowercase and duplicates the entry added in the regular section, which breaks the established UPPERCASE/MixedCase/mixed-domain-lowercase-local pattern used by every other provider.

_{Reviews (1): Last reviewed commit: "add proton mail case sensitiity test for..." | Re-trigger Greptile}

[greptile-apps]

The third entry in this group is all-lowercase (mymail777@proton.me), so it doesn't exercise any case normalisation — it is identical to the test added at line 564 in the regular block. Every other provider's three-entry group in this section follows the pattern UPPERCASE / MixedCase / lowercase-local+mixed-domain (e.g. user.name+tag@Protonmail.com). Using mymail777@Proton.Me as the third variant would stay consistent with that pattern and actually verify domain-case folding.

Suggested change

	['MYMAIL777@PROTON.ME', 'mymail777@protonmail.com'],
	['MyMail777@Proton.Me', 'mymail777@protonmail.com'],
	['mymail777@proton.me', 'mymail777@protonmail.com'],
	['MYMAIL777@PROTON.ME', 'mymail777@protonmail.com'],
	['MyMail777@Proton.Me', 'mymail777@protonmail.com'],
	['mymail777@Proton.Me', 'mymail777@protonmail.com'],