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.

web/src/lib/components/SystemHealthCard.svelte

@@ -1,8 +1,12 @@
 <!--
   Dashboard summary card: container counts and recent errors.
+
+  Workload-first: pulls running/total counts straight from the global
+  containers index instead of fanning out project → stage → instance
+  queries the way the legacy implementation did.
 -->
 <script lang="ts">
-	import type { Instance, EventLogStats } from '$lib/types';
+	import type { EventLogStats } from '$lib/types';
 	import * as api from '$lib/api';
 	import { IconServer, IconAlert } from '$lib/components/icons';
 	import { t } from '$lib/i18n';
@@ -13,37 +17,24 @@
 	let loading = $state(true);
 
 	$effect(() => {
-		let cancelled = false;
+		const ac = new AbortController();
 
 		async function load() {
 			try {
-				const [projects, eventStats] = await Promise.all([
-					api.listProjects(),
-					api.fetchEventLogStats().catch(() => ({ info: 0, warn: 0, error: 0, total: 0 }) as EventLogStats)
+				const [containers, eventStats] = await Promise.all([
+					api.listContainers({}, ac.signal).catch(() => []),
+					api.fetchEventLogStats(ac.signal).catch(
+						() => ({ info: 0, warn: 0, error: 0, total: 0 }) as EventLogStats
+					)
 				]);
 
-				// Gather all instances across projects/stages.
-				const allInstances: Instance[] = [];
-				for (const project of projects) {
-					try {
-						const detail = await api.getProject(project.id);
-						for (const stage of detail.stages ?? []) {
-							const instances = await api.listInstances(project.id, stage.id);
-							allInstances.push(...instances);
-						}
-					} catch {
-						// Skip projects that fail to load.
-					}
-				}
-
-				if (!cancelled) {
-					runningCount = allInstances.filter((i) => i.state === 'running').length;
-					stoppedCount = allInstances.filter((i) => i.state !== 'running').length;
-					recentErrors = eventStats.error;
-					loading = false;
-				}
+				if (ac.signal.aborted) return;
+				runningCount = containers.filter((c) => c.state === 'running').length;
+				stoppedCount = containers.filter((c) => c.state !== 'running').length;
+				recentErrors = eventStats.error;
+				loading = false;
 			} catch {
-				if (!cancelled) {
+				if (!ac.signal.aborted) {
 					loading = false;
 				}
 			}
@@ -51,9 +42,7 @@
 
 		load();
 
-		return () => {
-			cancelled = true;
-		};
+		return () => ac.abort();
 	});
 </script>
 
@@ -62,7 +51,7 @@
 		<h3 class="mb-4 text-sm font-semibold text-[var(--text-primary)]">{$t('systemHealth.title')}</h3>
 		<div class="grid grid-cols-1 gap-3 sm:grid-cols-2">
 			<!-- Containers -->
-			<a href="/projects" class="flex items-center gap-3 rounded-lg p-3 transition-colors hover:bg-[var(--surface-card-hover)]">
+			<a href="/containers" class="flex items-center gap-3 rounded-lg p-3 transition-colors hover:bg-[var(--surface-card-hover)]">
 				<div class="flex h-9 w-9 items-center justify-center rounded-lg bg-emerald-50 dark:bg-emerald-950/30 text-emerald-600">
 					<IconServer size={18} />
 				</div>