refactor: untrack generated python proto, regenerate in build

[Ma77Ball]

What changes were proposed in this PR?

Stop version-tracking the betterproto-generated Python files under amber/src/main/python/proto/. Add a genPythonProto sbt task that runs bin/python-proto-gen.sh as a dependency of WorkflowExecutionService/Compile/compile, with a graceful skip when protoc is missing. Wire protoc 3.19.4 (matching PB.protocVersion) and betterproto[compiler]==2.0.0b7 into the three image build stages (worker,master, web-app) and the three CI jobs that touch Python proto (python, python-state-materialization-mac, amber-integration). The 14th tracked file (proto/org/apache/texera/web/__init__.py) had no corresponding .proto source and is gone after regen; grep confirms no callers.

Any related issues, documentation, or discussions?

Closes: #4102

How was this PR tested?

locally: sbt clean WorkflowExecutionService/compile regenerates the tree and pytest -m "not integration" passes; skip path verified with protoc absent. All three Docker images build end-to-end. CI covers the workflow YAML on
push.

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

Co-authored with Claude Opus 4.7 in compliance with ASF

[Ma77Ball]

/request-review @Yicong-Huang

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 43.51%. Comparing base (bf2f92c) to head (ec349cb).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5077      +/-   ##
============================================
+ Coverage     43.35%   43.51%   +0.16%     
+ Complexity     2212     2210       -2     
============================================
  Files          1049     1051       +2     
  Lines         40560    40685     +125     
  Branches       4322     4322              
============================================
+ Hits          17583    17703     +120     
- Misses        21886    21887       +1     
- Partials       1091     1095       +4     

Flag	Coverage Δ
access-control-service	39.53% <ø> (ø)
agent-service	33.76% <ø> (ø)
amber	43.78% <ø> (-0.03%)	⬇️
computing-unit-managing-service	0.00% <ø> (ø)
config-service	0.00% <ø> (ø)
file-service	32.18% <ø> (ø)
frontend	34.61% <ø> (ø)
python	90.79% <ø> (+0.28%)	⬆️
workflow-compiling-service	56.81% <ø> (ø)

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[Yicong-Huang]

Thanks, that's a good direction for change! Let inline comments.

Please make pr description concise. The "how you test" section is basically saying "ci" can verify. I don't get too much new info reading it.

[Ma77Ball]

@Yicong-Huang, I addressed the comments. Please review when available.