[Gemini Log Analyzer] Part 2: Backend Infrastructure (Config, Models, & Database Flow)

[ievdokdm]

This is Part 2 of the stacked Pull Request series implementing the Gemini Log Analyzer feature.

Depends on Part 1 (already merged): #5042

This PR extracts the backend data flow, configuration, dynamic config flags, and serialization models from the API implementation branch into a clean infrastructure layer:

• Configures AppEngine service config and flags in config.yaml and generated dynamic config files.
• Implements database storage interface storeLogAnalysis in UnifiedCheckRun.
• Adds the logAnalysis field to the PresubmitJobResponse RPC models to serialize results.

Stacked PR Series:

• Part 1: Backend Foundation (Models & Setup) (Merged)
• Part 2: Backend Infrastructure (Config & Database Data Flow) (This PR)
• Part 3: Backend Core API (Genkit Logic & Handlers)
• Part 4: Frontend Dashboard UI

[eyebrowsoffire]

LGTM