[Security] Harden devConsoleAssetsMiddleware against path traversal

[gonzaloriestra]

WHY are these changes introduced?

The devConsoleAssetsMiddleware was vulnerable to path traversal attacks because it joined user-provided assetPath with the rootDirectory without validating that the resulting path remained within the intended directory.

WHAT is this pull request doing?

• Updated devConsoleAssetsMiddleware in packages/app/src/cli/services/dev/extension/server/middlewares.ts to use resolvePath and isSubpath for path validation.
• Added regression tests in packages/app/src/cli/services/dev/extension/server/middlewares.test.ts.
• Ensured proper use of utilities.sendError for error handling in the middleware.

How to test your changes?

CI handles testing. You can also run the specific tests:
pnpm --filter app vitest run src/cli/services/dev/extension/server/middlewares.test.ts

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type (patch for bug fixes · minor for new features · major for breaking changes) and added a changeset with pnpm changeset add

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PR created automatically by Jules for task 15346866280291798229 started by @gonzaloriestra

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