Refactor bottleneck analytics service

[ccf]

Summary

• Extract bottleneck, root-cause, recovery, and time-lost analytics into analytics_bottlenecks.py
• Keep analytics_service.get_bottleneck_analytics as a compatibility wrapper so existing callers and cache monkeypatch tests keep working
• Remove the bottleneck-specific constants and helper implementations from the shared analytics service

Verification

• ruff check src/primer/server/services/analytics_service.py src/primer/server/services/analytics_bottlenecks.py
• ruff format --check src/primer/server/services/analytics_service.py src/primer/server/services/analytics_bottlenecks.py
• pytest --import-mode=importlib tests/test_analytics.py -q
• ruff check .
• ruff format --check .
• bandit -r src/ -c pyproject.toml
• pytest --import-mode=importlib -q
• Pre-commit and pre-push hooks passed while committing/pushing

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Note

Medium Risk
Primarily a large refactor that moves complex analytics logic and caching behavior into a new module; risk is moderate due to potential subtle behavioral differences in queries/aggregation and cache wiring despite intended parity.

Overview
Refactors bottleneck analytics by moving friction impact, root-cause clustering, recovery, and time-lost calculations out of analytics_service.py into a new analytics_bottlenecks.py module.

analytics_service.get_bottleneck_analytics is now a thin compatibility wrapper that delegates to the new implementation while still using the existing cache helpers, and the bottleneck-specific constants/helpers are removed from the shared analytics service.

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