perf(cors): move cors before helmet and consolidate res.setHeader

[shenald-dev]

Moves cors() middleware to execute before helmet(). This enables preflight OPTIONS requests to be immediately intercepted and resolved without undergoing unnecessary security header processing, reducing baseline latency and CPU overhead. Also consolidates redundant res.setHeader calls in the JSON error handler into a single call.

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PR created automatically by Jules for task 4250582525074431202 started by @shenald-dev

[google-labs-jules]

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[shenald-dev]

Looks good, merging this in. CI is green and everything checks out 👍

Move CORS middleware before Helmet for faster preflight handling and consolidate duplicate header setting.

[google-labs-jules]

Looks good, merging this in. CI is green and everything checks out 👍

Move CORS middleware before Helmet for faster preflight handling and consolidate duplicate header setting.

Acknowledged.