Implement admin operations panel

[minorstep]

/claim #29

What changed

Replaced the placeholder admin panel with a mock-backed but functional admin operations surface for FreelanceFlow.

Backend

• Added server-side admin-role enforcement for every /api/admin/* route
• Replaced the single metrics stub with admin overview, users, moderation, disputes, settings, and audit endpoints
• Added paginated and filterable user, moderation, dispute, and audit responses
• Added user suspend, reinstate, and ban actions
• Added listing approve, reject, and escalate actions, including poster notification hooks for rejections
• Added dispute ruling actions for client, freelancer, refund, or senior-admin escalation
• Added platform controls for registrations and job posting, with audit logging
• Added append-only in-memory audit events for admin actions

Frontend

• Replaced /admin placeholder with a dense operations dashboard
• Added admin token gate, manual refresh, metrics, trust distribution, controls, user management, moderation, disputes, and audit log views
• Added accessible labels for filters and controls, loading/error-ready state, and responsive tables

Demo

Short demo video included at demos/admin-operations-panel-demo.mp4.

Validation

• node /tmp/codex-npm/package/bin/npm-cli.js test -w apps/api passed: 8 tests
• node node_modules/typescript/bin/tsc -p apps/web/tsconfig.json --noEmit --incremental false passed
• git diff --check passed
• Verified the demo MP4 decodes as a 9 second, 1280x720 H.264 video

Note: npm run build -w apps/web could not complete in this local Codex desktop environment because Next failed to load the local macOS SWC native binary from the external volume due to code-signature validation. The web TypeScript check passes.

[minorstep]

Thanks for the bounty. This PR is ready for review and the visible checks are passing. Please let me know if anything else is needed from me for review or reward processing.