test: add independent log parser fixtures

[brain-marchine]

Fixes #5

Summary

Add hand-written, independent log parser fixtures for JSON, plain text, and nginx access logs so parser regressions cannot false-pass against self-generated samples.

Changes

• Fixture files under tools/fixtures/log_parser/ sourced from representative archived log line shapes (not parser output).
• tests/test_log_parser_fixtures.py validates timestamp, level, service/format, and key fields; malformed lines are rejected without crashing.

Testing

• python3 -m pytest -q tests/test_log_parser_fixtures.py — 6 passed
• python3 build.py -m frailbox — diagnostic artifacts included (diagnostic/build-00000000.logd + .json)

Checklist

• Relevant modules affected by these changes build locally
• Tests pass locally
• Diagnostic build log is committed in this PR
• Documentation has been updated, if applicable
• Configuration or schema changes are documented, if applicable
• No generated build artifacts are committed, except the required diagnostic build log
• Changes are scoped to the PR purpose and avoid unrelated cleanup
• Security, privacy, and error-handling implications have been considered

Payout wallet (Base): 0x86D4FC06f553792D8c33058438Bcc7444182EB30