ci: port workflows from .github/ to .forgejo/ (Forgejo Actions)

GitHub torrentclaw org is shadow-banned and the CI lives at git.torrentclaw.com
now. Forgejo Actions is enabled cluster-wide; this moves the workflows into the
runner's natively-watched .forgejo/workflows/ tree and adapts each step so the
existing Forgejo runner ('docker', 'ubuntu-latest' labels) can execute them
without leaning on GitHub-only tooling.

- ci.yml: drop actions/setup-go (use container: golang:1.25), replace
  golangci-lint-action with the upstream install.sh, drop codecov-action
  (third-party, can re-add later with a Forgejo-compatible variant).
- release.yml: drop goreleaser-action (install via curl), wire GITEA_TOKEN +
  the new release.gitea_urls block in .goreleaser.yml so goreleaser publishes
  to Forgejo. Sign step swaps 'gh release upload' for curl against the Forgejo
  releases API (via the in-cluster forgejo:3000 hostname). VirusTotal job
  dropped — depended heavily on 'gh release' wiring; can be reimplemented
  against the Forgejo API later if we re-enable it.
- docker-rebuild.yml: drop docker/login-action + docker/build-push-action,
  use raw 'docker' commands with manually-installed buildx + qemu. Same
  weekly schedule (Mon 04:17 UTC) and same 'latest' refresh behaviour.
- pages.yml: deleted — install.sh / install.ps1 are already served from the
  Hetzner releases volume at torrentclaw.com/install.sh, so the GitHub Pages
  copy was redundant even before the shadow-ban.

.goreleaser.yml: add release.gitea_urls (api=forgejo:3000, download via the
public Forgejo URL) + prerelease:auto. ship.sh uses '--skip=publish' so local
runs aren't affected by the new release block.

.goreleaser.yml

@@ -59,6 +59,18 @@ changelog:
       - "^test:"
       - "^chore:"
 
+# Self-hosted Forgejo at git.torrentclaw.com. goreleaser detects GITEA_TOKEN +
+# these URLs and publishes the release there instead of GitHub. Reachable via
+# `forgejo` hostname inside the dokploy-network (the runner shares it); for
+# local goreleaser runs outside the network, override via env GITEA_API_URL.
+release:
+  gitea_urls:
+    api: http://forgejo:3000/api/v1
+    download: https://git.torrentclaw.com
+    skip_tls_verify: false
+  draft: false
+  prerelease: auto
+
 # Homebrew tap — requires PAT with repo scope (not GITHUB_TOKEN)
 # Enable when torrentclaw/homebrew-tap PAT is configured as HOMEBREW_TAP_TOKEN
 # brews: