feat(cutover): hard legacy cutover — drop projects/stacks/sites/deploys

The clean-break delete that closes the workload-first refactor arc.
Net diff: ~30 backend files deleted, ~20 modified, ~12k LOC removed
on the Go side; entire /projects /stacks /sites /deploy frontend
trees gone; ~6.7k LOC removed on the Svelte/TypeScript side.

Backend
- API handlers gone: internal/api/{projects,stages,stage_env,stacks,
  static_sites,deploys,instances,volume_browser}.go
- Store CRUD + tests gone: internal/store/{projects,stages,stage_env,
  stacks,static_sites,static_site_secrets,deploys,poll_state,volumes,
  workload_sync}.go (+ _test.go siblings)
- Legacy deployer pipeline gone: internal/deployer/{bluegreen,promote,
  rollback,subdomain,resolver_test}.go; deployer.go trimmed to just the
  dispatch surface used by the plugin pipeline
- internal/staticsite/{manager,healthcheck}.go and
  internal/stack/manager.go gone (the rest of those packages stay as
  helpers imported by the static + compose plugins)
- internal/registry/poller.go gone (legacy registry poller)
- internal/volume.ResolvePath gone; ResolveWorkloadPath stays
- internal/webhook: handleWebhook (project) + handleSiteWebhook (site)
  gone; only POST /api/webhook/triggers/{secret} remains
- workload-side webhook URL handlers (getWorkloadWebhook +
  regenerateWorkloadWebhook + EnsureWorkloadWebhookSecret +
  SetWorkloadWebhookSecret + GetWorkloadByWebhookSecret) gone — they
  minted URLs that would 404 against the new trigger-only ingress
- cmd/server/main.go: dropped staticsite.Manager, stack.Manager,
  staticsite.HealthChecker, registry poller, SetSiteSyncTriggerer,
  SetStaticSiteManager, SetStackManager, wireStaticBackend
- store/store.go: idempotent DROP TABLE IF EXISTS for every legacy
  table (projects, stages, stage_env, volumes, deploys, deploy_logs,
  poll_states, stacks, stack_revisions, stack_deploys, static_sites,
  static_site_secrets); FK order children-then-parents
- store/models.go: dropped Project, Stage, Deploy, DeployLog, StageEnv,
  Volume, StaticSite, StaticSiteSecret, Stack, StackRevision,
  StackDeploy types; kept WorkloadKind constants as documented strings
- internal/store/helpers.go (new): BoolToInt, rowScanner,
  GenerateWebhookSecret extracted from deleted CRUD files
- internal/api/secrets.go (new): forwards to store.GenerateWebhookSecret
  so api + store paths share one secret-generation impl (no
  panic-vs-UUID-fallback divergence)
- internal/reconciler/reconciler.go: dropped legacy stack-by-compose
  + static-site label paths; only canonical tinyforge.workload.id
  dispatch remains
- providers (gitea_content/github_provider/gitlab_provider) gained
  path-traversal rejection on every tree entry
- internal/webhook ParsedImage / ParseImageRef demoted to package-
  private (no external callers)

Frontend
- /projects /stacks /sites /deploy routes deleted (entire trees)
- ProjectCard / InstanceCard / StaleContainerCard components deleted
- api.ts: dropped every project/stage/stack/site/deploy/instance
  helper + types (Project, Stage, Stack, StaticSite, Deploy,
  Instance, Volume, etc.); kept Workload, Container, App, Settings,
  Registry, EventTrigger, LogScanRule, webhook envelopes
- WorkloadWebhook type + getWorkloadWebhook/regenerateWorkloadWebhook
  api functions gone (mirror of the backend deletion above)
- web/src/routes/+layout.svelte: dropped /projects /sites /stacks
  /deploy nav entries, trimmed quick-nav keymap
- web/src/routes/+page.svelte: dashboard rewrite — reads
  listWorkloads + listContainers only; 4-card stat grid
  (workloads/running/failed/stale) + recent workloads strip
- navCounts.ts, SystemHealthCard.svelte, ContainerLogs.svelte,
  ContainerStats.svelte, StatusBadge.svelte, TagCombobox.svelte,
  proxies/+page.svelte, containers/+page.svelte all rewired to the
  workload-first surface
- AbortController plumbing on dashboard, nav-counts, stale page,
  SystemHealthCard so navigation doesn't leave dangling fetches
- i18n: dropped projects.*, projectDetail.*, envEditor.*,
  volumeEditor.*, volumeBrowser.*, quickDeploy.*, sites.*, stacks.*,
  instance.*, confirm.* namespaces; en/ru parity preserved (1042
  keys each)

Hardening from go-reviewer + security-reviewer + typescript-reviewer
subagent passes (0 CRITICAL across all three; 1 HIGH + ~12 MEDIUM
addressed inline before commit):

- Sec H1: dead-end workload webhook URL handlers (would mint URLs
  that 404 the new trigger-only ingress) deleted across backend +
  frontend
- Go M1: IsTerminalDeployStatus dropped (no production callers)
- Go M2: ParsedImage/ParseImageRef lowercased (in-package only)
- Go M6: generateWebhookSecret unified — api shim forwards to
  store.GenerateWebhookSecret
- Doc/comment freshness: stage_id (no longer FK), ProxyRoute legacy
  field names, workloadIDRow rationale, webhook_deliveries.target_type
  enum, WebhookDeliveryLog component header

Doc
- WORKLOAD_REFACTOR_TODO: cutover marked DONE; all three Priority 1
  items are now shipped. Next focus is Priority 3 polish (apps.* i18n
  + codemap entries) and Priority 4 tests.

Behavioral notes for operators upgrading from a pre-cutover build
- Existing rows in the dropped tables disappear on first boot.
- Legacy webhook URLs at /api/webhook/{secret} and
  /api/webhook/sites/{secret} return 404; CI configs must repoint to
  /api/webhook/triggers/{secret} (the trigger-split boot backfill
  lifted any embedded workload secret onto a Trigger row, so the
  secret value itself carries over).
- Frontend routes /projects /stacks /sites /deploy are gone; nav
  links replaced with /apps and /triggers.

internal/api/workload_env.go

@@ -136,61 +136,12 @@ func (s *Server) deleteWorkloadEnv(w http.ResponseWriter, r *http.Request) {
 	respondJSON(w, http.StatusOK, map[string]string{"deleted": envID})
 }
 
-// getWorkloadWebhook handles GET /api/workloads/{id}/webhook. Returns
-// the canonical URL + secret + signature-state flags. Lazily generates
-// a secret if the workload row predates the column.
-func (s *Server) getWorkloadWebhook(w http.ResponseWriter, r *http.Request) {
-	id := chi.URLParam(r, "id")
-	secret, err := s.store.EnsureWorkloadWebhookSecret(id)
-	if err != nil {
-		if errors.Is(err, store.ErrNotFound) {
-			respondNotFound(w, "workload")
-			return
-		}
-		slog.Error("ensure workload webhook secret", "workload", id, "error", err)
-		respondError(w, http.StatusInternalServerError, "failed to get webhook secret")
-		return
-	}
-	row, err := s.store.GetWorkloadByID(id)
-	if err != nil {
-		respondError(w, http.StatusInternalServerError, "failed to get workload")
-		return
-	}
-	respondJSON(w, http.StatusOK, webhookURLResponse{
-		WebhookURL:              "/api/webhook/workloads/" + secret,
-		WebhookSecret:           secret,
-		HasSigningSecret:        row.WebhookSigningSecret != "",
-		WebhookRequireSignature: row.WebhookRequireSignature,
-	})
-}
-
-// regenerateWorkloadWebhook handles POST /api/workloads/{id}/webhook/regenerate.
-// Rotates the URL secret. The old secret is invalidated immediately —
-// any external system still hitting the old URL gets a 404 on next call.
-func (s *Server) regenerateWorkloadWebhook(w http.ResponseWriter, r *http.Request) {
-	id := chi.URLParam(r, "id")
-	if _, err := s.store.GetWorkloadByID(id); err != nil {
-		if errors.Is(err, store.ErrNotFound) {
-			respondNotFound(w, "workload")
-			return
-		}
-		respondError(w, http.StatusInternalServerError, "failed to get workload")
-		return
-	}
-	secret := generateWebhookSecret()
-	if err := s.store.SetWorkloadWebhookSecret(id, secret); err != nil {
-		slog.Error("rotate workload webhook secret", "workload", id, "error", err)
-		respondError(w, http.StatusInternalServerError, "failed to rotate webhook secret")
-		return
-	}
-	row, _ := s.store.GetWorkloadByID(id)
-	respondJSON(w, http.StatusOK, webhookURLResponse{
-		WebhookURL:              "/api/webhook/workloads/" + secret,
-		WebhookSecret:           secret,
-		HasSigningSecret:        row.WebhookSigningSecret != "",
-		WebhookRequireSignature: row.WebhookRequireSignature,
-	})
-}
+// Workload-level webhook URL handlers were dropped in the hard legacy
+// cutover: the old `/api/webhook/workloads/{secret}` route is gone, so
+// minting a workload secret would hand operators a URL that 404s. The
+// inbound webhook surface is now exclusively first-class triggers
+// (`/api/webhook/triggers/{secret}`); use the trigger CRUD + bindings
+// endpoints to wire a workload to inbound deploys.
 
 // validEnvKey accepts POSIX-style env names. Rejects anything that would
 // confuse Docker's env parser (=, spaces, control chars).