feat: return object id in TUS upload completion response header

[oniani1]

Closes #647

Summary

After a TUS resumable upload completes, there's currently no way to get the object_id of the uploaded file without making a follow-up .list() call. The onSuccess callback from tus-js-client only gets the upload URL, not the object ID.

The standard POST /object endpoint already returns the ID in the JSON body ({ Id, Key }). For TUS, since the response format is governed by the protocol, a response header is the natural fit -- same approach @fenos suggested in #647.

This captures the return value of completeUpload() in the onUploadFinish lifecycle hook and includes the object's UUID in a new x-supabase-id response header. The @tus/server library already supports custom headers -- both PatchHandler and PostHandler merge them into the outgoing response.

Changes

• src/http/routes/tus/lifecycle.ts -- capture completeUpload() result, add x-supabase-id header
• src/test/tus.test.ts -- new test verifying the header is present, is a valid UUID, and matches the database record

Test plan

• Added test: TUS upload completion returns x-supabase-id header with valid UUID matching DB record
• Existing TUS tests pass with no regressions

[coveralls]

Coverage Report for CI Build 24208084802

Coverage decreased (-0.001%) to 80.842%

Details

• Coverage decreased (-0.001%) from the base build.
• Patch coverage: 2 of 2 lines across 1 file are fully covered (100%).
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	37226
Covered Lines:	30272
Line Coverage:	81.32%
Relevant Branches:	4141
Covered Branches:	3170
Branch Coverage:	76.55%
Branches in Coverage %:	Yes
Coverage Strength:	320.47 hits per line

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