feat: wire Forgejo Actions CI/CD workflows (#22)
- ci.yml: API lint (ruff F+I) + pytest, web vue-tsc + vitest + build
- mirror.yml: push to GitHub (CircuitForgeLLC) + Codeberg (CircuitForge) on main/tags
- release.yml: Docker build → Forgejo registry + release via API; GHCR deferred pending BSL policy (cf-agents#3)
- .cliff.toml: git-cliff changelog config for semver releases
- pyproject.toml: add [dev] extras (pytest, ruff), ruff config
- Fix 45 ruff violations across codebase (import sorting, unused vars, unused imports)