Add unit tests for BDVCountryNameAndCode methods

[devin-ai-integration]

Summary

Adds 53 unit tests covering all public methods, with primary focus on the new getCountrySuffixForPrefix: method. Tests are built and run via GNUstep on Linux using a simple make test command.

Changes

Test file (BDVCountryNameAndCodeTests.m):

• getCountrySuffixForPrefix: — 6 test groups: unique dial codes, shared dial codes (e.g. +44 → GB/GG/IM/JE), string dial codes (e.g. "+1 684"), no-match, nil input, multiple shared codes (+61, +1, +47)
• prefixForCountryCode: — known codes, case-insensitivity, non-existent code
• countryNameAtIndex: — first/second entry, out-of-bounds
• allCountryNames / allPrefixDialingCodes — count validation, spot checks
• initWithPlistPath: — invalid path, nil path edge cases

Source changes (backwards-compatible):

• Added initWithPlistPath: designated initializer for testability
• Added helper accessors: prefixForCountryCode:, countryNameAtIndex:, allCountryNames, allPrefixDialingCodes
• Changed getCountrySuffixForPrefix: parameter type from NSString * to id (plist stores dial codes as both NSNumber and NSString)
• Guarded UIImage usage with __has_include(<UIKit/UIKit.h>) for cross-platform compilation
• Moved ivars from @implementation block to @interface for GNU runtime compatibility
• Extracted loadPlistFromPath: to share init logic between init and initWithPlistPath:

Build infrastructure:

• Makefile — make test builds and runs the test suite
• .gitignore — excludes build artifacts

Review & Testing Checklist for Human

• Verify the new initWithPlistPath: initializer doesn't break existing init behavior when used from NSBundle (Xcode/iOS)
• Confirm getCountrySuffixForPrefix: type change from NSString * to id is compatible with existing callers
• Run make test locally to verify all 53 tests pass

Notes

All 53 tests pass on Ubuntu/GNUstep. The UIImage-dependent countryFlagForCurrentLocale method is excluded from testing on Linux (guarded by __has_include).

Link to Devin session: https://app.devin.ai/sessions/eff22b773a6d4323ba77f2886839fde8
Requested by: @basdvries

[devin-ai-integration]

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