feat: add R2 traffic logging to Workers

[leocuisine]

Summary

• Add the shared R2 traffic logger and attach it to the REST API and MCP Workers.
• Bind both Workers to the ps-wiki R2 bucket as TRAFFIC_LOGS.
• Preserve existing route, middleware, response, and error-handling logic.

Validation

• npx wrangler types passed for both Worker configurations and generated TRAFFIC_LOGS: R2Bucket.
• npm run typecheck passed.
• npm test passed: 7 tests.
• npx wrangler deploy --dry-run --config wrangler.toml passed.
• npx wrangler deploy --dry-run --config wrangler-mcp.toml passed.
• git diff --check passed.

No deployment was performed.