feat(ui): nav app persistente nel masthead (desktop + drawer mobile)

L'utente non aveva modo di saltare da una pagina app all'altra senza tornare alla home (solo il logo era cliccabile). Aggiunta nav globale:

- **Desktop**: row di link orizzontale a destra del logo (Cucina · Tracking · Digiuno · Spesa · Profilo · Abbonamento). Pagina corrente evidenziata in pomodoro, hover sulle altre.
- **Mobile**: bottone hamburger (≡ Menu) che apre un drawer sotto la riga di header con le 6 voci. Si chiude da solo al cambio di pathname.

`<Masthead>` ora è un Client Component (serve usePathname). Prop `showNav` (default false) controlla la nav: attivata sulle 7 pagine logged-in (`/`, /plan, /tracking, /fasting, /shopping, /profile, /billing, /recipes/[id]). Lasciata off su welcome, onboarding, sign-in, sign-up.

Aggiunti i18n keys: navPlan/navTracking/navFasting/navShopping/navProfile/navBilling. Rimossi gli `issueLabel="N. XX — ..."" dalle pagine app (`issueLabel` resta supportato per pagine senza nav).

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

apps/web/src/app/[locale]/billing/page.tsx

@@ -39,7 +39,7 @@ function BillingPageContent({ status }: { status: BillingStatus | null }) {
     return (
       <div className="relative">
         <div className="min-h-screen w-full px-6 sm:px-10 lg:px-16 xl:px-24">
-          <Masthead issueLabel="N. 08 — Abbonamento" />
+          <Masthead showNav />
           <main className="pb-24 pt-12">
             <p className="editorial-eyebrow">{t('errorLoading')}</p>
           </main>
@@ -54,7 +54,7 @@ function BillingPageContent({ status }: { status: BillingStatus | null }) {
   return (
     <div className="relative">
       <div className="min-h-screen w-full px-6 sm:px-10 lg:px-16 xl:px-24">
-        <Masthead issueLabel="N. 08 — Abbonamento" />
+        <Masthead showNav />
         <main className="relative overflow-hidden pb-24 pt-10 sm:pt-12">
           <CursorGlow color="hsl(var(--oro))" size={520} />
           <div

apps/web/src/app/[locale]/fasting/page.tsx

@@ -44,7 +44,7 @@ function FastingPageContent({
   return (
     <div className="relative">
       <div className="min-h-screen w-full px-6 sm:px-10 lg:px-16 xl:px-24">
-        <Masthead issueLabel="N. 07 — Digiuno" />
+        <Masthead showNav />
         <main className="relative overflow-hidden pb-24 pt-10 sm:pt-12">
           <CursorGlow color="hsl(var(--pomodoro))" size={520} />
           <div

apps/web/src/app/[locale]/page.tsx

@@ -28,7 +28,7 @@ function HomeContent({
   return (
     <div className="relative">
       <div className="min-h-screen w-full px-6 sm:px-10 lg:px-16 xl:px-24">
-        <Masthead />
+        <Masthead showNav={!!userName} />
         {userName ? (
           <SignedInDashboard userName={userName} billing={billing} />
         ) : (

apps/web/src/app/[locale]/plan/page.tsx

@@ -64,7 +64,7 @@ function PlanPageContent({
   return (
     <div className="relative">
       <div className="min-h-screen w-full px-6 sm:px-10 lg:px-16 xl:px-24">
-        <Masthead issueLabel="N. 05 — Cucina" />
+        <Masthead showNav />
         <main className="relative overflow-hidden py-10 sm:py-12">
           <CursorGlow color="hsl(var(--pomodoro))" size={520} />
           <div

apps/web/src/app/[locale]/profile/page.tsx

@@ -59,7 +59,7 @@ function ProfilePageContent({
   return (
     <div className="relative">
       <div className="min-h-screen w-full px-6 sm:px-10 lg:px-16 xl:px-24">
-        <Masthead issueLabel="N. 04 — Profilo" />
+        <Masthead showNav />
         <main className="relative overflow-hidden pb-24 pt-10 sm:pt-12">
           <CursorGlow color="hsl(var(--oliva))" size={520} />
           <div

apps/web/src/app/[locale]/recipes/[id]/page.tsx

@@ -111,7 +111,7 @@ function RecipeContent({ recipe }: { recipe: RecipeView }) {
 
   return (
     <div className="min-h-screen w-full px-6 sm:px-10 lg:px-16 xl:px-24">
-      <Masthead issueLabel={`N. 08 — ${t(`categoryLabel.${recipe.category}`)}`} />
+      <Masthead showNav />
       <main className="py-10 sm:py-14">
         <Link
           href="/plan"

apps/web/src/app/[locale]/shopping/page.tsx

@@ -54,7 +54,7 @@ function ShoppingPageContent({ list }: { list: ShoppingList | null }) {
   return (
     <div className="relative">
       <div className="min-h-screen w-full px-6 sm:px-10 lg:px-16 xl:px-24">
-        <Masthead issueLabel="N. 09 — La spesa" />
+        <Masthead showNav />
         <main className="relative overflow-hidden pb-24 pt-10 sm:pt-12">
           <CursorGlow color="hsl(var(--oliva))" size={520} />
           <div

apps/web/src/app/[locale]/tracking/page.tsx

@@ -73,7 +73,7 @@ function TrackingPageContent({
   return (
     <div className="relative">
       <div className="min-h-screen w-full px-6 sm:px-10 lg:px-16 xl:px-24">
-        <Masthead issueLabel="N. 06 — Tracking" />
+        <Masthead showNav />
         <main className="relative overflow-hidden pb-24 pt-10 sm:pt-12">
           <CursorGlow color="hsl(var(--oro))" size={520} />
           <div