[Design] Upgrade all Python projects to 3.14 and all Go projects to 1.26

[duanhongyi]

Background
We need to standardize runtime versions across all projects: Python to 3.14, Go to 1.26, for consistency, performance, and maintainability.

Goals

• Upgrade version baseline across all repos/services
• Update CI, build images, and dependency workflows accordingly
• Minimize regression risk and keep rollback path clear

Scope

1. Inventory
   • List Python services/scripts/tools
   • List Go services/CLIs/libraries
   • List all base/build images
2. Python 3.14 design
   • Update pyproject.toml / requirements constraints
   • Build compatibility matrix for dependencies
   • Align tooling (pytest/mypy/ruff, etc.)
3. Go 1.26 design
   • Update go.mod go directive
   • Refresh dependencies + static analysis compatibility
   • Review build flags, cross-compile, CGO impacts
4. CI/CD and container images
   • Upgrade GitHub Actions/CI runtime setup
   • Update Dockerfiles/base images
   • Adjust pip/go cache strategy
5. Rollout and rollback
   • Batch rollout by project tier
   • Canary + regression verification
   • Rollback playbook per service

Definition of Done

• All Python projects build/test with 3.14 by default
• All Go projects build/test with 1.26 by default
• Critical services pass regression/performance validation
• Upgrade docs (compatibility, known issues, rollback) are complete
• At least one production rollout drill is completed

Risks / Notes

• Third-party packages not yet compatible
• Runtime/compiler behavior changes causing edge regressions
• Cross-repo upgrade sequencing complexity