feat: Docker diagnostic hints on disconnection

- Classify Docker errors into categories (socket_not_found, connection_refused,
  permission_denied, timeout, tls_error) with platform-specific hints
- Enrich GET /api/health with structured diagnostics (category, hints, platform)
- Expandable hints panel in sidebar when Docker is disconnected
- "Retry now" button for immediate re-check
- Collapsible raw error details for advanced users

web/src/lib/api.ts

@@ -3,6 +3,7 @@ import type {
 	ContainerStats,
 	Deploy,
 	DeployLog,
+	DockerHealth,
 	EventLogEntry,
 	EventLogStats,
 	InspectResult,
@@ -267,8 +268,8 @@ export function listNpmCertificates(): Promise<NpmCertificate[]> {
 
 // ── Health ──────────────────────────────────────────────────────────
 
-export function getHealth(): Promise<{ docker: boolean }> {
-	return get<{ docker: boolean }>('/api/health');
+export function getHealth(): Promise<{ docker: DockerHealth }> {
+	return get<{ docker: DockerHealth }>('/api/health');
 }
 
 // ── Auth ─────────────────────────────────────────────────────────────