feat(dashboard): add presigned URL upload flow to dashboard API

[coderabbitai]

Summary

PR #129 (#129) introduced a presigned URL three-step upload architecture for the public API to avoid proxying large file bytes through the Node.js server. The dashboard side (apps/dashboard-api/) currently has no storage routes and was not included in that PR.

This issue tracks implementing the same flow for the dashboard.

Work Required

• Add storage routes to apps/dashboard-api/ (e.g., /upload-request and /upload-confirm).
• Wire in appropriate authentication/authorization middleware suitable for dashboard users (session-based or similar, rather than verifyApiKey/requireSecretKey).
• Reuse the shared getPresignedUploadUrl and verifyUploadedFile helpers already exported from @urbackend/common (added in PR feat(storage): replace proxy upload with presigned URL architecture #129).
• Apply the same quota-check-before and quota-charge-after-confirm pattern used in the public API controller.
• Add/update dashboard-specific tests.
• Document any required CORS PUT configuration for S3/R2 buckets if not already covered.

References

• Implementing PR: feat(storage): replace proxy upload with presigned URL architecture #129
• Requested by: @yash-pouranik
• Related comment: feat(storage): replace proxy upload with presigned URL architecture #129 (comment)

[yash-pouranik]

@Nitin-kumar-yadav1307
This is follow up issue for PR #129
Assigning to you.

[Nitin-kumar-yadav1307]

Ok