Implement Channel and Chaincode core functionality

[dodo920306]

Summary

Implement core functionality for Channel and Chaincode, including creation, listing, uploading, and committing operations.

Changes

Channel

• Implement Channel creation API
• Add channel/service.py to handle Channel logic
• Remove legacy Channel code

Chaincode

• Implement Chaincode listing API
• Implement Chaincode upload functionality
• Implement Chaincode creation functionality
• Implement Chaincode commit functionality
• Add chaincode/service.py to handle Chaincode logic

Cleanup

• Remove redundant legacy API files
• Create database migrations

API Endpoints

• POST /api/channels/ - Create Channel
• GET /api/chaincodes/ - List Chaincodes
• POST /api/chaincodes/ - Create Chaincode
• POST /api/chaincodes/{id}/upload/ - Upload Chaincode
• POST /api/chaincodes/{id}/commit/ - Commit Chaincode

Dependencies

• Depends on: Restructure backend into separate Django applications #742

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🤖 This PR description was generated with AI assistance (Claude, Anthropic).

[dodo920306]

This is draft only because #742 hasn't been merged yet.

[dodo920306]

@yeasy Please review and merge this.