feat: add quality checks, event fixtures, latency tracking, and refresh state

[iamtjbest]

Summary

• Add automated formatting, linting, and static-analysis checks for pull requests.
• Add reusable blockchain event test fixtures covering valid, duplicate, missing-field, unsupported-version, and malformed-event cases.
• Add notification delivery latency tracking and aggregation.
• Add a non-blocking dashboard refresh state indicator while preserving existing event data during refresh.

Issues

Closes #809
Closes #810
Closes #805
Closes #650

Validation

• git diff --check passes.
• Relevant formatting and fixture validation was performed.
• Dashboard refresh behavior is covered by tests.
• Existing unrelated listener syntax errors were left untouched to maintain strict issue scope.

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