[feat][backend] ob add manual annotation

[kidkidkid]

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[codecov]

Codecov Report

❌ Patch coverage is 80.14184% with 56 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ckend/modules/observability/infra/repo/ck/spans.go	72.31%	28 Missing and 21 partials ⚠️
.../modules/observability/infra/repo/ck/annotation.go	93.33%	3 Missing and 4 partials ⚠️

@@            Coverage Diff             @@
##             main     #194      +/-   ##
==========================================
+ Coverage   68.02%   68.37%   +0.35%     
==========================================
  Files         568      568              
  Lines       50484    50742     +258     
==========================================
+ Hits        34342    34697     +355     
+ Misses      13473    13348     -125     
- Partials     2669     2697      +28     

Flag	Coverage Δ
unittests	68.37% <80.14%> (+0.35%)	⬆️

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Files with missing lines	Coverage Δ
.../modules/observability/infra/repo/ck/annotation.go	90.17% <93.33%> (+90.17%)	⬆️
...ckend/modules/observability/infra/repo/ck/spans.go	72.70% <72.31%> (+31.01%)	⬆️

... and 6 files with indirect coverage changes

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[CozeLoop]

Aime code review: added inline comments for correctness and robustness in spans.go (nil-map assignment; filters nil-guard; annoTable validation) and annotation.go (retry backoff). Please see the inline comments for actionable fixes.