feat(berths): inline spec-PDF preview, manual-pin badge, maintenance module toggle, under-offer popover

Post-cutover UAT batch #3:
- #62 Spec tab renders the current berth spec PDF inline (lazy PdfViewer,
  toggleable, default-open) + explicit download. Interest Documents tab
  already previews/downloads linked deal docs inline (verified).
- #57 Surface berths.status_override_mode through the interest-berths API;
  linked-berth rows show an amber "Pin overrides pitch" badge + corrected
  consequence copy when a berth is specifically-pitched but manually pinned
  (the soft-pin wins on the public map).
- #63 New maintenance-module gate (maintenance_module_enabled, default on):
  registry + admin Settings toggle, maintenance-module.service, port-provider
  useMaintenanceModuleEnabled, layout wiring, buildBerthTabs hides the
  Maintenance tab when off, and both maintenance log routes assert the gate.
- #66 BerthOccupancyChip: >1 competing interest opens a popover listing every
  deal (name + stage + in-EOI/primary + link); single stays a direct link.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/admin/settings/settings-manager.tsx

@@ -72,6 +72,14 @@ const KNOWN_SETTINGS: Array<{
     type: 'boolean',
     defaultValue: true,
   },
+  {
+    key: 'maintenance_module_enabled',
+    label: 'Berth Maintenance Module',
+    description:
+      'Enable the per-berth maintenance log (the "Maintenance" tab on each berth detail page). On by default. Disabling hides the Maintenance tab everywhere and blocks its log routes; previously-recorded maintenance logs are preserved and reappear when you re-enable.',
+    type: 'boolean',
+    defaultValue: true,
+  },
   {
     key: 'ai_interest_scoring',
     label: 'AI Interest Scoring',