BNN-13 Implement requirements validation for bounty submissions

[median-app]

Median Task: BNN-13

Develop and integrate a feature into the GitHub app to automatically validate bounty submissions against predefined requirement criteria before allowing them to be processed.

[tiago918]

Opened PR #44: #44

Implements a focused requirement validator for bounty submissions and wires the validation result into fake-bounty catch metadata before processing. Verification included core tests, core typecheck, targeted Prettier check, and git diff --check.

[shuibui]

/submit 46

[bountydotnew]

@shuibui bounty.new is in early access. Link your GitHub account at https://bounty.new/integrations to get started.