[feat][backend] Add prompt management OpenAPI endpoints for CRUD, draft and commit operations

[lizwang11]

This PR introduces a complete set of Prompt Management OpenAPI endpoints, extending the existing prompt OpenAPI service (which previously only supported Execute, ExecuteStreaming, ListPromptBasic, and BatchGetPromptByPromptKey) with 6 new management APIs:

New API Endpoints:

Method Path Description POST /v1/loop/prompts Create a new prompt with name, key, description, type, and security level DELETE /v1/loop/prompts/:prompt_id Delete a prompt by ID GET /v1/loop/prompts/:prompt_id Get prompt details (optionally with commit and/or draft info) POST /v1/loop/prompts/:prompt_id/drafts/save Save a prompt draft POST /v1/loop/prompts/:prompt_id/drafts/commit Commit a prompt draft with version and description POST /v1/loop/prompts/:prompt_id/commits/list List prompt commit history with pagination

[codecov]

Codecov Report

❌ Patch coverage is 70.64516% with 91 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...les/prompt/application/convertor/openapi_manage.go	46.37%	66 Missing and 8 partials ⚠️
...i/handler/coze/loop/apis/prompt_open_apiservice.go	0.00%	12 Missing ⚠️
backend/modules/prompt/application/openapi.go	96.87%	3 Missing and 2 partials ⚠️

❌ Your patch status has failed because the patch coverage (70.64%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

@@            Coverage Diff             @@
##             main     #474      +/-   ##
==========================================
- Coverage   75.07%   75.07%   -0.01%     
==========================================
  Files         632      633       +1     
  Lines       67215    67521     +306     
==========================================
+ Hits        50464    50693     +229     
- Misses      13523    13594      +71     
- Partials     3228     3234       +6     

Flag	Coverage Δ
unittests	75.07% <70.64%> (-0.01%)	⬇️

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Files with missing lines	Coverage Δ
backend/modules/prompt/application/openapi.go	91.44% <96.87%> (+3.31%)	⬆️
...i/handler/coze/loop/apis/prompt_open_apiservice.go	0.00% <0.00%> (ø)
...les/prompt/application/convertor/openapi_manage.go	46.37% <46.37%> (ø)

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