fix: generate API from published module

[casey-brooks]

Summary

• switch buf.gen.yaml back to the published buf.build/agynio/api module now that the API contract is available
• avoid requiring git inside the Docker build image for npm run generate

Fixes #98

Validation

• nix shell nixpkgs#nodejs_20 -c sh -c 'npm ci && npm run generate && npm run lint && npm run typecheck && npm run test && npm run build'
  • Tests: 72 passed, 0 failed, 0 skipped across 18 files
  • Lint: passed with no errors
• nix shell nixpkgs#docker-buildx -c docker-buildx build --progress=plain --target build -t console-app-release-fix:test .
  • Docker build target passed; npm run generate and npm run build completed in the image