Aggiorna marketing: prezzi lancio, Funzionalità narrativa e link store.

Allinea i piani Light/Full ai prezzi di lancio, ripensa /funzionalita per vendere il prodotto e aggiunge i badge App Store/Play nella home.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/services/billing/stripe/price_catalog.rb

@@ -4,9 +4,16 @@ module Billing
       INTERVALS = %w[monthly yearly].freeze
       DEFAULT_INTERVAL = "yearly"
 
-      PRICING = {
-        "premium_light" => { "yearly" => "€40/anno", "monthly" => "€5/mese" },
-        "premium_full" => { "yearly" => "€200/anno", "monthly" => "€20/mese" }
+      # Importi in centesimi (EUR). Il yearly è il prezzo lancio addebitato.
+      AMOUNTS = {
+        "premium_light" => {
+          "yearly" => { charge: 5900, list: 7900, equivalent_monthly: 492 },
+          "monthly" => { charge: 790 }
+        },
+        "premium_full" => {
+          "yearly" => { charge: 19_900, list: 24_900, equivalent_monthly: 1658 },
+          "monthly" => { charge: 2490 }
+        }
       }.freeze
 
       class << self
@@ -30,7 +37,23 @@ module Billing
         end
 
         def label(plan_slug:, interval:)
-          PRICING.dig(plan_slug.to_s, normalize_interval(interval)) || normalize_interval(interval)
+          interval = normalize_interval(interval)
+          format_interval_price(charge_cents(plan_slug, interval), interval)
+        end
+
+        def list_label(plan_slug:, interval: "yearly")
+          interval = normalize_interval(interval)
+          cents = list_cents(plan_slug, interval)
+          return nil if cents.blank?
+
+          format_interval_price(cents, interval)
+        end
+
+        def equivalent_monthly_label(plan_slug:)
+          cents = AMOUNTS.dig(plan_slug.to_s, "yearly", :equivalent_monthly)
+          return nil if cents.blank?
+
+          format_interval_price(cents, "monthly")
         end
 
         def available_intervals(plan_slug:)
@@ -52,8 +75,33 @@ module Billing
           nil
         end
 
+        def format_eur(cents)
+          cents = cents.to_i
+          whole, frac = cents.divmod(100)
+          if frac.zero?
+            "€#{whole}"
+          else
+            sep = I18n.locale.to_s == "en" ? "." : ","
+            "€#{whole}#{sep}#{frac.to_s.rjust(2, '0')}"
+          end
+        end
+
         private
 
+        def charge_cents(plan_slug, interval)
+          AMOUNTS.dig(plan_slug.to_s, interval, :charge)
+        end
+
+        def list_cents(plan_slug, interval)
+          AMOUNTS.dig(plan_slug.to_s, interval, :list)
+        end
+
+        def format_interval_price(cents, interval)
+          return nil if cents.blank?
+
+          I18n.t("billing.prices.#{interval}", amount: format_eur(cents))
+        end
+
         def price_id_for(plan_slug, interval)
           case [plan_slug, interval]
           when %w[premium_light monthly]