feat(canary): unified Justfile with frontend + backend + compose groups
Replaces template Justfile (which referenced ./react-scss/). Groups:
[frontend] pnpm install/dev/build/preview, biome, stylelint, tsc
Targets at fe-install/fe-dev/fe-build/fe-preview prefixed for clarity
[backend] go mod tidy, vet, golangci-lint, test (unit + integration tags),
coverage HTML, run, static build, air hot reload
[lint] lint = be-lint + biome + stylelint + tsc; ci = lint + test
[compose] docker compose lifecycle for prod (up/start/down/stop/build/logs/ps)
[tunnel] overlay with cloudflared.compose.yml for prod+tunnel
[dev] docker compose lifecycle for dev.compose.yml
[util] init (gen secrets + fetch GeoLite2), ports, info, clean
Justfile parses cleanly via 'just --list'. Frontend dir reference fixed
(now ./frontend, not ./react-scss).