fix: match Brazilian caller IDs to contacts regardless of country/operator code prefix

[brunogamacatao]

Summary

In Brazil, carriers deliver caller ID for the very same phone line in several inconsistent formats, e.g.:

• +55<DDD><number> (with country code)
• 0<operator code><DDD><number> (with a long-distance carrier/operator selection code, e.g. 015 for Vivo)
• <DDD><number> (no country code)
• <number> (no DDD at all)

Because SimpleCallScreeningService relies on the exact/native contact lookup (SimpleContactsHelper.existsSync, which in turn uses the OS PhoneLookup provider and PhoneNumberUtils.compare), these format variations frequently fail to match against a contact saved with a different formatting, even though it's the same physical number. This makes the "only allow calls from contacts" setting unreliable for Brazilian users — legitimate calls from saved contacts get blocked as "unknown".

There's an additional wrinkle: Brazil made a 9th digit mandatory for all mobile numbers starting in 2016. Contacts saved before that migration may still have the old 8-digit format, while an incoming call is reported using the current 9-digit format (or vice versa).

Solution

• Added BrazilianPhoneNumberMatcher, a small pure-Kotlin utility that parses a raw number into DDD + subscriber number, discarding country code and operator code (which are never a stable part of the number). It disambiguates mobile (9 digits, always starting with 9) vs. landline (8 digits) subscriber numbers, and compares only the last 8 digits when one side is in the old 8-digit mobile format and the other in the current 9-digit format.
• SimpleCallScreeningService now falls back to this comparison — against both system and private ("my contacts") phone numbers — only when the existing lookup returns a definite "not found", preserving all current behavior (including the "undetermined"/no-permission case, which still allows the call through).
• Added unit tests (BrazilianPhoneNumberMatcherTest) covering country code, operator code, trunk prefix, formatting characters, DDD/number mismatches, and the 8-digit vs 9-digit mobile format transition.

Test plan

• ./gradlew :app:testFossDebugUnitTest — all tests pass
• ./gradlew :app:assembleFossDebug — builds successfully
• Manually installed on a physical device (Android, foss flavor) with "only allow calls from contacts" enabled, and confirmed a real incoming call from a saved contact — previously misdetected as unknown due to carrier-added prefixes — is now correctly recognized and allowed through

🤖 Generated with Claude Code

[fossifybot]

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