feat(tenancies-p6): module-gate entity tabs (berth / client / yacht)

- PortProvider exposes tenanciesModuleByPort + a useTenanciesModuleEnabled()
  hook that returns the flag for the currently-active port. Synchronous
  read off context (server-resolved in the dashboard layout), so no
  fetch latency / hydration flicker when the rep flips ports.
- buildBerthTabs / getClientTabs / getYachtTabs gain a
  tenanciesModuleEnabled option. When false, the Tenancies tab is
  filtered out entirely. When true, it slots into the entity-specific
  position (after Interests on berth + yacht; after Companies on client).
- BerthDetail / ClientDetail / YachtDetail pass the hook value through.
  Hook call ordered above the early-return so React's rules-of-hooks
  stays satisfied. Existing read-only tab content (Active tenancy card
  + History + the berth-side BerthReserveDialog "Create tenancy" CTA
  from P2) stays untouched — it just becomes visible when the module
  is on.

Deferred (separate ship): generic TenancyCreateDialog that pre-fills
clientId / yachtId from the parent entity context, so client / yacht
tabs can mint a tenancy without bouncing through the berth detail page.
Today client/yacht Tenancies tabs are read-only (the create entry-point
is the berth tab); the generic dialog will land alongside the Edit /
Renew / Transfer / End dialogs (design § P6 sub-tasks).

Verified: tsc clean, 1493/1493 vitest.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/yachts/yacht-tabs.tsx

@@ -355,8 +355,13 @@ function YachtTenanciesTab({ yachtId }: { yachtId: string }) {
   );
 }
 
-export function getYachtTabs({ yachtId, currentUserId, yacht }: YachtTabsOptions): DetailTab[] {
-  return [
+export function getYachtTabs({
+  yachtId,
+  currentUserId,
+  yacht,
+  tenanciesModuleEnabled = false,
+}: YachtTabsOptions & { tenanciesModuleEnabled?: boolean }): DetailTab[] {
+  const tabs: DetailTab[] = [
     {
       id: 'overview',
       label: 'Overview',
@@ -372,11 +377,6 @@ export function getYachtTabs({ yachtId, currentUserId, yacht }: YachtTabsOptions
       label: 'Interests',
       content: <YachtInterestsTab yachtId={yachtId} />,
     },
-    {
-      id: 'tenancies',
-      label: 'Tenancies',
-      content: <YachtTenanciesTab yachtId={yachtId} />,
-    },
     {
       id: 'notes',
       label: 'Notes',
@@ -401,4 +401,14 @@ export function getYachtTabs({ yachtId, currentUserId, yacht }: YachtTabsOptions
       ),
     },
   ];
+  if (tenanciesModuleEnabled) {
+    // Insert after Interests (index 3) so the ordering reads:
+    // Overview → Ownership History → Interests → Tenancies.
+    tabs.splice(3, 0, {
+      id: 'tenancies',
+      label: 'Tenancies',
+      content: <YachtTenanciesTab yachtId={yachtId} />,
+    });
+  }
+  return tabs;
 }