Fix ModuleNotFoundError for integrations package

[LokiMetaSmith]

The application was failing to start with a ModuleNotFoundError: No module named 'integrations'.
This was caused by pipecatapp/integrations lacking an __init__.py file, preventing Python from treating it as a package in the deployment environment.
This change creates an empty pipecatapp/integrations/__init__.py to explicitly mark the directory as a package.
Verified by creating a script that attempts the import and confirming it proceeds past the module lookup (failing later on missing dependencies in the test environment, which confirms the module was found).

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PR created automatically by Jules for task 13198800040126701617 started by @LokiMetaSmith

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