fix: dia-1287: single kafka producer for app

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Commit https://github.com/HumanSignal/infra/commit/df3f68b29a4781a46338950a37e40bec9effe249 is created.

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Codecov Report

Attention: Patch coverage is 9.09091% with 30 lines in your changes missing coverage. Please review.

Project coverage is 57.31%. Comparing base (bc69ce6) to head (877855a). Report is 11 commits behind head on master.

Files	Patch %	Lines
server/app.py	6.66%	28 Missing :warning:
server/handlers/result_handlers.py	0.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #160 +/- ## ========================================== - Coverage 57.75% 57.31% -0.45% ========================================== Files 40 41 +1 Lines 1754 1778 +24 ========================================== + Hits 1013 1019 +6 - Misses 741 759 +18 ```

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Commit https://github.com/HumanSignal/infra/commit/54590f9e86cf0a39f4b3fbb4f282aa933d9d9bfb is created.

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Commit https://github.com/HumanSignal/infra/commit/a4f9e9b9de4dc537fe888d93c608b4828a3972f8 is created.

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Commit https://github.com/HumanSignal/infra/commit/eabf4466b8176607a42fe30ad998792664f986e7 is created.

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Commit https://github.com/HumanSignal/infra/commit/aed494c9126795a1ddf65420d7e907b59cf820ac is created.