feat(static): inline static-source plugin; drop phantom-row adapter

Lift the static-site deploy pipeline from internal/staticsite/manager.go
into internal/workload/plugin/source/static/ so plugin-native static
workloads operate directly on plugin.Workload + the containers table +
workload_env. The cmd/server/static_backend.go phantom-row adapter is
gone; the legacy static_sites table is no longer touched on plugin
deploys.

Backend
- new state.go: runtimeState (last_commit_sha, last_sync_at,
  last_error, status) persisted in containers.extra_json under the
  deterministic row id <workloadID>:site
- per-workload sync.Mutex serializes saveState read-modify-write so
  parallel deploys for the same workload can't race container_id /
  proxy_route_id writes
- extra_json round-trips through map[string]json.RawMessage so
  unknown keys survive — typed runtimeStateKeys are stripped before
  merge so clearing a typed field actually drops the key
- new env.go reads workload_env (replaces static_site_secrets for
  plugin-native sites); decrypt-failure logs and skips one entry
  rather than failing the whole deploy
- new build.go ports prepareDenoBuild + prepareStaticBuild + copyDir;
  copyDir uses filepath.WalkDir + Lstat to refuse symlinks and
  non-regular files
- new deploy.go is the ~300-line core; intent.Reason gates force vs
  skip-if-no-changes; success-path saveState failure rolls back
  container + proxy route and writes "failed" state (no orphans)
- new teardown.go combines Remove + Stop; idempotent on
  never-deployed workloads
- new reconcile.go refreshes container state from Docker; flips
  runtimeState.Status to failed when the container is missing/crashed

Hardening (from go-reviewer + security-reviewer subagent passes;
1 CRITICAL + 5 HIGH + 3 MEDIUM addressed before merge)
- path-traversal defense in all 3 providers (gitea_content,
  github_provider, gitlab_provider): reject tree entries whose
  resolved local path escapes destDir
- verifyDownloadInsideRoot walks the build dir post-download as a
  second line of defense
- sanitizeError redacts the access token, collapses to one line, and
  clamps to 240 bytes before persisting to extra_json or fanning out
  to the notification webhook
- container/image/volume names suffixed with workload-id short prefix
  (workload name is not UNIQUE in schema)
- primaryDomain reads settings.Domain to complete a bare subdomain
  face into a full FQDN (matches legacy Manager behavior)
- ctx-aware health-check sleep
- json.Marshal for event metadata (was fmt.Sprintf JSON template)
- strings.HasPrefix for failed-status detection (was brittle slice
  expression)

Wire-up
- cmd/server/main.go: removed wireStaticBackend(...) call; existing
  blank import on _ ".../source/static" drives init() registration
- cmd/server/static_backend.go deleted

Doc
- WORKLOAD_REFACTOR_TODO: static port marked DONE; next focus is
  the hard legacy cutover (drop /api/projects, /api/stacks,
  /api/sites, /api/stages + their tables, internal/stack +
  internal/staticsite packages, frontend /projects /stacks /sites)

Behavior notes for operators
- plugin-native static workloads no longer write to static_sites;
  legacy /api/sites/* still serves original rows unchanged
- legacy tinyforge.static-site / .static-site-name container labels
  dropped on plugin deploys; canonical tinyforge.workload.id / .kind
  cover ownership
- container/image/volume names gained an 8-char ID suffix
  (e.g. dw-site-mysite-a1b2c3d4); legacy-deployed sites keep the
  old shape until redeployed through the plugin path

internal/staticsite/github_provider.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"os"
 	"path/filepath"
 	"strings"
 	"time"
@@ -221,6 +222,15 @@ func (g *GitHubProvider) DownloadFolder(ctx context.Context, owner, repo, branch
 		relativePath := strings.TrimPrefix(entry.Path, prefix)
 		localPath := filepath.Join(destDir, filepath.FromSlash(relativePath))
 
+		// Path-traversal defense: refuse tree entries whose resolved
+		// path escapes destDir. A hostile/compromised GHE could
+		// otherwise deliver `..`-laden entries.
+		cleanDest := filepath.Clean(destDir)
+		if cleanRel := filepath.Clean(localPath); cleanRel != cleanDest &&
+			!strings.HasPrefix(cleanRel, cleanDest+string(os.PathSeparator)) {
+			return fmt.Errorf("rejecting tree entry outside dest: %s", relativePath)
+		}
+
 		// GitHub raw content URL.
 		// For github.com: https://raw.githubusercontent.com/{owner}/{repo}/{branch}/{path}
 		// For GHE: {baseURL}/{owner}/{repo}/raw/{branch}/{path}