[feat][trace] support logid in trace tree search

[fankuo]

Summary

• add optional logid to SearchTraceTreeOApiRequest
• resolve trace time range from log ID and forward it to trace search
• keep existing trace ID behavior and pagination unchanged

Testing

• focused observability application tests
• PPE smoke: 1,000 unique span IDs, fetched as 10 concurrent batches of 100; exact set match

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

@@           Coverage Diff           @@
##             main     #668   +/-   ##
=======================================
  Coverage   78.82%   78.83%           
=======================================
  Files         707      707           
  Lines       87823    87824    +1     
=======================================
+ Hits        69227    69233    +6     
+ Misses      14607    14603    -4     
+ Partials     3989     3988    -1     

Flag	Coverage Δ
unittests	78.83% <100.00%> (+<0.01%)	⬆️

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

Files with missing lines	Coverage Δ
...ckend/modules/observability/application/openapi.go	86.22% <100.00%> (+0.59%)	⬆️

... and 2 files with indirect coverage changes

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