[feat][backend] ob metrics new

[kidkidkid]

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[CozeLoop]

Aime code review: posted inline comments on concurrency correctness in compound metrics, an unimplemented UpsertAnnotation stub, and logging verbosity. Overall, the new metrics architecture and CK DAO additions look sound and align with Go idioms and safety practices.

[codecov]

Codecov Report

❌ Patch coverage is 84.61954% with 285 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ules/observability/domain/metric/service/metric.go	68.15%	73 Missing and 34 partials ⚠️
...ckend/modules/observability/infra/repo/ck/spans.go	0.00%	83 Missing ⚠️
...ce/metric/model/model_output_token_count_metric.go	0.00%	24 Missing ⚠️
.../metric/service/metric/wrapper/multiple_wrapper.go	0.00%	19 Missing ⚠️
...ackend/modules/observability/application/metric.go	85.82%	13 Missing and 5 partials ⚠️
...main/metric/service/metric/wrapper/self_wrapper.go	25.00%	12 Missing ⚠️
.../observability/application/convertor/trace/span.go	68.00%	4 Missing and 4 partials ⚠️
backend/modules/observability/infra/repo/trace.go	76.92%	6 Missing ⚠️
...ler/coze/loop/apis/observability_metric_service.go	0.00%	4 Missing ⚠️
backend/api/handler/coze/loop/apis/handler.go	0.00%	2 Missing ⚠️
... and 1 more

@@            Coverage Diff             @@
##             main     #268      +/-   ##
==========================================
+ Coverage   66.98%   67.63%   +0.65%     
==========================================
  Files         507      565      +58     
  Lines       47839    49672    +1833     
==========================================
+ Hits        32045    33598    +1553     
- Misses      13186    13424     +238     
- Partials     2608     2650      +42     

Flag	Coverage Δ
unittests	67.63% <84.61%> (+0.65%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
backend/infra/ck/ck.go	0.00% <ø> (ø)
...servability/application/convertor/metric/metric.go	100.00% <100.00%> (ø)
...bility/application/convertor/trace/trace_export.go	95.73% <ø> (ø)
...dules/observability/domain/metric/entity/metric.go	100.00% <100.00%> (ø)
...ervice/metric/general/general_fail_ratio_metric.go	100.00% <100.00%> (ø)
.../metric/general/general_model_fail_ratio_metric.go	100.00% <100.00%> (ø)
...ice/metric/general/general_model_latency_metric.go	100.00% <100.00%> (ø)
...etric/general/general_model_total_tokens_metric.go	100.00% <100.00%> (ø)
...e/metric/general/general_tool_fail_ratio_metric.go	100.00% <100.00%> (ø)
...vice/metric/general/general_tool_latency_metric.go	100.00% <100.00%> (ø)
... and 55 more

... and 2 files with indirect coverage changes

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