Fix Flask health endpoint collision

[Pigbibi]

Summary

• avoid registering duplicate Flask endpoint names for health routes
• keep /health and /healthz available on platforms with custom health checks
• rename or isolate endpoint functions so they do not collide with the QPK health shim

Root cause

Cloud Run workers failed at import time with AssertionError: View function mapping is overwriting an existing endpoint function: health after register_health_endpoint(app) and local route functions both used endpoint name health.

Validation

• python -m py_compile main.py
• uvx ruff check main.py
• static route-collision assertions