feat(observability): traces end-to-end (gateway + UI panel)

[Ma77Ball]

What changes were proposed in this PR?

Distributed-trace retrieval through the gateway plus a trace-tree UI panel.
Backend:

• Trace query builder and parseTraces.
• TracesResource exposing trace retrieval by id, with id validation and scope enforcement at the gateway.
  Frontend:
• Traces panel rendering spans as a tree built from parent-span relationships, with pivot-from-log so a log row can open its trace directly. Span fields are bound with text interpolation only.

Any related issues, documentation, or discussions?

Closes: #5373
Part of #4070. Stacked on #5380.

How was this PR tested?

• Backend specs for the trace query builder and parser; sbt scalafmtCheckAll passes.
• Frontend traces-panel specs, including the span-tree builder; prettier-eslint and eslint pass.
• Compile and the full test suites run in this PR's CI.

Was this PR authored or co-authored using generative AI tooling?

Co-authored with Claude Opus 4.8 in compliance with ASF

[codecov-commenter]

Codecov Report

❌ Patch coverage is 59.74026% with 744 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.32%. Comparing base (6d31f46) to head (ae477e7).
⚠️ Report is 52 commits behind head on main.

Files with missing lines	Patch %	Lines
...observability/gateway/ObservabilityResources.scala	0.00%	273 Missing ⚠️
...observability/logs-panel/logs-panel.component.html	56.71%	58 Missing ⚠️
...ala/org/apache/texera/observability/OtelInit.scala	63.30%	43 Missing and 8 partials ⚠️
...apache/texera/web/observability/gateway/dtos.scala	76.59%	38 Missing and 6 partials ⚠️
...texera/web/observability/gateway/AuditLogger.scala	0.00%	41 Missing ⚠️
...xera/web/observability/gateway/ScopeResolver.scala	19.44%	27 Missing and 2 partials ⚠️
...ra/web/observability/gateway/ResponseParsers.scala	77.96%	10 Missing and 16 partials ⚠️
...era/web/observability/gateway/GatewayContext.scala	0.00%	21 Missing ⚠️
...web/observability/gateway/WorkflowRunCounter.scala	0.00%	20 Missing ⚠️
...a/org/apache/texera/web/TexeraWebApplication.scala	0.00%	18 Missing ⚠️
... and 26 more

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5381      +/-   ##
============================================
+ Coverage     53.86%   55.32%   +1.45%     
- Complexity     2756     3015     +259     
============================================
  Files          1099     1149      +50     
  Lines         42541    45065    +2524     
  Branches       4577     5016     +439     
============================================
+ Hits          22916    24932    +2016     
- Misses        18290    18643     +353     
- Partials       1335     1490     +155     

Flag	Coverage Δ		*Carryforward flag
access-control-service	70.14% <100.00%> (-0.30%)	⬇️
agent-service	34.36% <ø> (ø)		Carriedforward from 818e316
amber	57.19% <55.03%> (+1.99%)	⬆️
computing-unit-managing-service	0.00% <0.00%> (-1.66%)	⬇️
config-service	50.76% <40.00%> (-5.95%)	⬇️
file-service	58.88% <68.96%> (+1.81%)	⬆️
frontend	49.66% <74.86%> (+1.61%)	⬆️
notebook-migration-service	78.57% <ø> (?)
pyamber	90.15% <100.00%> (+0.02%)	⬆️	Carriedforward from 818e316
python	90.76% <ø> (-0.04%)	⬇️	Carriedforward from 818e316
workflow-compiling-service	54.74% <ø> (-3.96%)	⬇️

*This pull request uses carry forward flags. Click here to find out more.

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[github-actions]

Automated Reviewer Suggestions

Based on the git blame history of the changed files, we recommend the following reviewers:

• Contributors with relevant context: @bobbai00, @aicam, @Yicong-Huang
  You can notify them by mentioning @bobbai00, @aicam, @Yicong-Huang in a comment.