fix(android): cap ANR stack traces to reduce OOM risk

[robert-northmind]

Description

This change bounds how much of the main thread stack we stringify when the in-app ANR watchdog fires. Deep Flutter stacks can be very large; building and logging unbounded strings on low-memory devices contributed to OutOfMemoryError during ANR capture (see #174).

• Cap at 128 frames and 64 KiB for the stored stack trace string.
• Add JSON fields: stacktrace_truncated, stacktrace_total_frames, stacktrace_included_frames.
• Replace full-stack Log.w with a short summary (included/total frames, truncated flag).
• Extract AnrStackTraceFormatter (pure Java) with JUnit tests in android/anr-stack-formatter-tests; CI runs ./gradlew :anr-stack-formatter-tests:test. The formatter guarantees the returned string length never exceeds maxChars (including truncation suffix).

Related Issue(s)

Fixes #174

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation
• Performance improvement
• Code refactoring
• Chore / Housekeeping

Checklist

• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have updated the CHANGELOG.md under the "Unreleased" section

Additional Notes

TDD-style: tests were added for max frame count, max character budget, and global length bound; a follow-up fix ensures the formatted string is hard-capped at maxChars when the truncation note would otherwise exceed the limit.

dart tool/pre_release_check.dart passes locally.

  

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