feat: add ModelScope backend support with modelscope:// protocol

[pmady]

What this PR does / why we need it:

Adds a new backend for downloading models and datasets from ModelScope Hub using the modelscope:// URL scheme, similar to the existing Hugging Face backend.

URL Format

modelscope://[<repo_type>/]<owner>/<repo>[/<path>][@<revision>]

Examples

# Download a model repository
dfget modelscope://inclusionAI/Ling-1T -O /tmp/ling-1t/ --recursive

# Download a single file
dfget modelscope://inclusionAI/Ling-1T/config.json -O /tmp/config.json

# Download with authentication
dfget modelscope://inclusionAI/Ling-1T/config.json -O /tmp/config.json --ms-token=<token>

# Download a dataset
dfget modelscope://datasets/damo/squad-zh/train.json -O /tmp/train.json

# Download from a specific revision
dfget modelscope://inclusionAI/Ling-1T/config.json@v1.0 -O /tmp/config.json

Features

• Support for models and datasets repository types
• File listing via ModelScope API (/api/v1/models/{id}/repo/files) for recursive downloads
• File download via ModelScope API (/api/v1/models/{id}/repo?FilePath=...)
• Authentication via --ms-token CLI flag (injected as Authorization: Bearer header)
• Range download support
• Default revision is master (matching ModelScope convention)

Which issue(s) this PR fixes:

Closes dragonflyoss/dragonfly#4420

Does this PR introduce a user-facing change?

Yes. Users can now download files and repositories from ModelScope Hub using dfget modelscope://... with P2P acceleration.

[pmady]

Hi maintainers, could you please add the enhancement label to this PR? The PR Label check requires one of: bug, enhancement, documentation, or dependencies. Thank you!

[codecov]

Codecov Report

❌ Patch coverage is 44.52055% with 405 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.26%. Comparing base (3c7d0d4) to head (cc744bf).
⚠️ Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
dragonfly-client-backend/src/model_scope.rs	43.11%	376 Missing ⚠️
dragonfly-client/src/bin/dfget/main.rs	40.00%	12 Missing ⚠️
dragonfly-client/src/resource/persistent_task.rs	0.00%	6 Missing ⚠️
dragonfly-client/src/resource/task.rs	0.00%	6 Missing ⚠️
dragonfly-client/src/grpc/dfdaemon_download.rs	0.00%	2 Missing ⚠️
dragonfly-client/src/grpc/dfdaemon_upload.rs	0.00%	2 Missing ⚠️
dragonfly-client-backend/src/hugging_face.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1673      +/-   ##
==========================================
- Coverage   50.46%   50.26%   -0.20%     
==========================================
  Files          85       86       +1     
  Lines       21224    21950     +726     
==========================================
+ Hits        10711    11034     +323     
- Misses      10513    10916     +403     

Files with missing lines	Coverage Δ
dragonfly-client-backend/src/http.rs	97.73% <100.00%> (+0.04%)	⬆️
dragonfly-client-backend/src/lib.rs	96.30% <100.00%> (+0.20%)	⬆️
dragonfly-client/src/resource/piece.rs	57.94% <ø> (ø)
dragonfly-client-backend/src/hugging_face.rs	35.80% <0.00%> (-0.06%)	⬇️
dragonfly-client/src/grpc/dfdaemon_download.rs	4.66% <0.00%> (-0.01%)	⬇️
dragonfly-client/src/grpc/dfdaemon_upload.rs	0.00% <0.00%> (ø)
dragonfly-client/src/resource/persistent_task.rs	0.00% <0.00%> (ø)
dragonfly-client/src/resource/task.rs	7.26% <0.00%> (-0.08%)	⬇️
dragonfly-client/src/bin/dfget/main.rs	49.59% <40.00%> (-0.15%)	⬇️
dragonfly-client-backend/src/model_scope.rs	43.11% <43.11%> (ø)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[gaius-qi]

@pmady Thanks, I'll finish the review by this week.