fix: enable chunked blob upload for Azure ACR replication

[xrkolovos]

Summary

Fixes #23015 — Azure ACR replication fails with HTTP 413 for blob layers larger than ~20MB.
Related: #21640

Root cause

Three issues were identified:

1. Missing adapter capability declaration — The Azure ACR adapter's Info() method did not set SupportedCopyByChunk: true, so the replication flow always defaulted to monolithic (single PUT) blob uploads for ACR destinations.

2. Copy flow ignores adapter capability — The copy flow (flow/copy.go) only checked the policy-level CopyByChunk flag and ignored the destination adapter's SupportedCopyByChunk declaration. Even if an adapter declared chunk support, users had to manually enable it per replication policy — a setting that is not exposed in the UI for non-Harbor registries.

3. req.ContentLength not set in PushBlobChunk() — The registry client set Content-Length via req.Header.Set(), but Go's HTTP client ignores manually set Content-Length headers. It uses the req.ContentLength struct field to decide between sending a Content-Length header or using Transfer-Encoding: chunked. Without setting req.ContentLength, Go sent blob chunks with HTTP chunked transfer encoding, which Azure ACR rejects with CONTENT_LENGTH_INVALID (400).

Changes

File	Change
src/pkg/reg/adapter/azurecr/adapter.go	Set SupportedCopyByChunk: true in Info()
src/controller/replication/flow/copy.go	Auto-enable chunked upload when destination adapter declares SupportedCopyByChunk support
src/pkg/registry/client.go	Set req.ContentLength in PushBlobChunk() to ensure proper Content-Length header

Testing

• Unit tests — Updated existing tests for the adapter and copy flow, including a new test case (TestCopyByChunkAutoEnabled) that validates auto-enabling chunked uploads based on adapter capability.
• Integration test — Added integration_test.go that performs a real 25MB chunked blob upload (5 × 5MB chunks) against a live Azure Container Registry instance. The test is skipped unless ACR_URL, ACR_USER, and ACR_PASS environment variables are set.

=== RUN   TestChunkedUploadToACR/chunked_upload_succeeds
    Uploading chunk 0-5242879 (5242880 bytes, last=false)
    OK - new location length: 328
    Uploading chunk 5242880-10485759 (5242880 bytes, last=false)
    OK - new location length: 336
    Uploading chunk 10485760-15728639 (5242880 bytes, last=false)
    OK - new location length: 336
    Uploading chunk 15728640-20971519 (5242880 bytes, last=false)
    OK - new location length: 336
    Uploading chunk 20971520-26214399 (5242880 bytes, last=true)
    OK - new location length: 106
    === SUCCESS: Chunked upload to Azure ACR works! ===
--- PASS: TestChunkedUploadToACR (6.09s)

How to run integration test

ACR_URL=https://yourregistry.azurecr.io ACR_USER=admin ACR_PASS=secret \
  go test -v -run TestChunkedUploadToACR ./src/pkg/reg/adapter/azurecr/...