backend: Update deployment config on app start

[tianjing-li]

AI Description

This PR introduces changes to the deployment configuration process, primarily involving the deployment_service module. The key modifications include:

• Renaming the update_config function to update_db_config in src/backend/routers/deployment.py and src/backend/services/deployment.py.
• Replacing deployment_service.update_config with deployment_service.update_db_config in the update_config function in src/backend/routers/deployment.py.
• Adding a new function update_db_config_from_env in src/backend/services/deployment.py to update the database configuration from the environment.
• Updating the test_update_config_db and test_update_config_no_db_deployments test functions in src/backend/tests/unit/services/test_deployment.py to use the new update_db_config function.
• Importing the get_session function from backend.database_models.database and calling deployment_service.update_db_config_from_env(next(get_session())) in src/backend/main.py.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 66.66667% with 7 lines in your changes missing coverage. Please review.

Project coverage is 77.25%. Comparing base (ec0c043) to head (5f884ca).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/backend/services/deployment.py	53.33%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #921      +/-   ##
==========================================
- Coverage   77.26%   77.25%   -0.01%     
==========================================
  Files         281      281              
  Lines       11485    11502      +17     
==========================================
+ Hits         8874     8886      +12     
- Misses       2611     2616       +5     

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