refactor(workload): finalize containers index + post-review hardening

Wraps up the workload refactor with the fixes that came out of the multi-agent
code review (see docs/plans/workload-refactor.md "What actually shipped").

Backend:
- store.ReconcileContainer: separate write path so the 30s reconciler tick no
  longer overwrites deployer-owned fields (subdomain, proxy_route_id,
  npm_proxy_id, image_tag).
- Container.stage_id column + index; ListProxyRoutes / ListContainersByStageID
  join via stage_id (survives stage rename), with legacy fallback to
  (project_id, role=stage_name).
- Reconciler: workload-existence check (rejects forged tinyforge.workload.id
  labels), skips inventing project-kind rows, child-context cancel before
  wg.Wait() on shutdown.
- Transactional CRUD across projects / stacks / static_sites: parent UPDATE
  and workload sync land in one transaction so secret rotations are durable.
- Webhook routing reads exclusively through workloads.webhook_secret; legacy
  GetProjectByWebhookSecret / GetStaticSiteByWebhookSecret fallback removed.
- store.GetStackByComposeProjectName + indexed lookup (no more full-table
  stack scan per compose container per tick).
- store.ListMissingSweepRows: filtered query for the missing-sweep.
- /api/instances/* handlers verify (workload_id, role) match URL
  (project_id, stage_name) before mutating — closes the cross-project
  hijack the security review flagged.
- extra_json no longer referenced from Go (column kept on disk for now).

Frontend:
- WorkloadContainers.svelte: generic detail-page panel reusable by stack and
  site detail pages.
- Containers page polish: client-side kind/state filters over an unfiltered
  fetch, URL-synced filters, race-safe loads via sequence number, EN+RU i18n,
  sidebar counter via navCounts.containers.

Misc:
- scripts/dev-server.sh: tolerate empty netstat grep result.
- .gitignore: ignore docker-watcher binaries, .claude/worktrees/, .facts-sync.json.

internal/api/stale.go

@@ -1,6 +1,7 @@
 package api
 
 import (
+	"encoding/json"
 	"errors"
 	"log/slog"
 	"net/http"
@@ -136,11 +137,25 @@ func (s *Server) cleanupContainer(r *http.Request, c store.Container) error {
 func (s *Server) emitStaleCleanupEvent(c store.Container) {
 	msg := "Stale container cleaned up: " + c.ID + " (tag: " + c.ImageTag + ")"
 
+	// Use json.Marshal — c.Role is reconciler-derived from a Docker label and
+	// could contain quotes / control chars that break a hand-built JSON string.
+	metaBytes, err := json.Marshal(map[string]string{
+		"container_id": c.ID,
+		"workload_id":  c.WorkloadID,
+		"role":         c.Role,
+	})
+	if err != nil {
+		// json.Marshal on a flat string map can only fail in pathological
+		// circumstances (memory exhaustion); fall back to an empty object so
+		// the event still records.
+		metaBytes = []byte(`{}`)
+	}
+
 	evt, err := s.store.InsertEvent(store.EventLog{
 		Source:   "stale_cleanup",
 		Severity: "info",
 		Message:  msg,
-		Metadata: `{"container_id":"` + c.ID + `","workload_id":"` + c.WorkloadID + `","role":"` + c.Role + `"}`,
+		Metadata: string(metaBytes),
 	})
 	if err != nil {
 		slog.Error("stale cleanup: failed to persist event", "error", err)