fix: require non-null uid in insertNewExecution

[Ma77Ball]

What changes were proposed in this PR?

• ExecutionsMetadataPersistService.insertNewExecution kept its uid: Option[Integer] signature but replaced setUid(uid.orNull) with setUid(uid.getOrElse(throw new IllegalArgumentException(...))), so a missing uid is rejected with a clear error instead of writing null into the NOT NULL workflow_executions.uid column (which produced a cryptic jOOQ DataAccessException).
• No .orNull is used; the caller (WorkflowService.initExecutionService) passes the Option through unchanged.
• Updated ExecutionsMetadataPersistServiceSpec: the missing-uid case now passes None and asserts an IllegalArgumentException is raised.

Any related issues, documentation, or discussions?

Closes: #5212

How was this PR tested?

• Compiled amber main + test sources under JDK 17 (clean).
• Ran WorkflowExecutionService/testOnly ...ExecutionsMetadataPersistServiceSpec: all 9 tests pass.
• Ran sbt scalafmtAll (clean).

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 55.55556% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.95%. Comparing base (eb287f3) to head (6eeac99).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...rg/apache/texera/web/service/WorkflowService.scala	0.00%	3 Missing ⚠️
...web/service/ExecutionsMetadataPersistService.scala	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5300      +/-   ##
============================================
- Coverage     49.97%   49.95%   -0.02%     
+ Complexity     2421     2417       -4     
============================================
  Files          1052     1052              
  Lines         40780    40786       +6     
  Branches       4356     4357       +1     
============================================
- Hits          20378    20376       -2     
- Misses        19193    19198       +5     
- Partials       1209     1212       +3     

Flag	Coverage Δ		*Carryforward flag
access-control-service	41.89% <ø> (ø)		Carriedforward from eb287f3
agent-service	33.76% <ø> (ø)		Carriedforward from eb287f3
amber	51.98% <55.55%> (-0.04%)	⬇️
computing-unit-managing-service	1.38% <ø> (ø)		Carriedforward from eb287f3
config-service	54.68% <ø> (ø)		Carriedforward from eb287f3
file-service	38.42% <ø> (ø)		Carriedforward from eb287f3
frontend	42.43% <ø> (ø)		Carriedforward from eb287f3
pyamber	90.80% <ø> (ø)		Carriedforward from eb287f3
python	90.80% <ø> (ø)		Carriedforward from eb287f3
workflow-compiling-service	58.39% <ø> (ø)		Carriedforward from eb287f3

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[Yicong-Huang]

Left comments inline. we should reject bad frontend requests.

[Yicong-Huang]

Approved with a nit, see inline.