i18n: add quotaModal block in en/es/pt-br/zh-cn (10 keys × 4 langs)

The quota-exhausted modal (rendered by the velxio.dev pro overlay when
a free user hits the daily AI cap) was hardcoded English. The modal is
seen by users from CN/BR/MX/CO/AR/PE/IN — the audiences most likely to
bounce on English-only UX. This adds the four key languages.

Keys:
  titleFree    — "You've hit today's free limit"
  titlePaid    — "You've reached your daily limit"
  bodyFree     — explainer + Pro upgrade pitch (interpolates cap/proCap/multiplier)
  bodyPaid     — explainer for paid users who hit their own tier's cap
  today / thisMonth / resets — stats labels
  ctaUpgrade   — primary CTA ("Upgrade to Pro — $15/mo")
  ctaSeePlans  — fallback CTA for non-free users
  ctaWait      — secondary "Wait until reset"

Upstream-only change — the velxio-prod overlay's AgentChatPanel.tsx is
wired to consume these via useTranslation in a separate commit.

🤖 Generated with Claude Code

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/i18n/locales/en/common.json

@@ -402,5 +402,17 @@
         "failed": "Registration failed."
       }
     }
+  },
+  "quotaModal": {
+    "titleFree": "You've hit today's free limit",
+    "titlePaid": "You've reached your daily limit",
+    "bodyFree": "Free accounts get {{cap}} AI messages a day. Pro ($15/mo) gives you {{proCap}}/day — {{multiplier}}× the cap. Or wait until your quota resets.",
+    "bodyPaid": "Your {{plan}} plan allows {{cap}} messages per day. Upgrade to a higher tier or wait for the reset.",
+    "today": "Today",
+    "thisMonth": "This month",
+    "resets": "Resets",
+    "ctaUpgrade": "Upgrade to Pro — $15/mo",
+    "ctaSeePlans": "See plans",
+    "ctaWait": "Wait until reset"
   }
 }

frontend/src/i18n/locales/es/common.json

@@ -402,5 +402,17 @@
         "failed": "Error al registrarse."
       }
     }
+  },
+  "quotaModal": {
+    "titleFree": "Llegaste al límite gratuito de hoy",
+    "titlePaid": "Alcanzaste tu límite diario",
+    "bodyFree": "Las cuentas Free reciben {{cap}} mensajes de IA por día. Pro ($15/mes) te da {{proCap}}/día — {{multiplier}}× el límite. O esperá hasta que se reinicie tu cuota.",
+    "bodyPaid": "Tu plan {{plan}} permite {{cap}} mensajes por día. Subí a un plan superior o esperá al reinicio.",
+    "today": "Hoy",
+    "thisMonth": "Este mes",
+    "resets": "Se reinicia",
+    "ctaUpgrade": "Pasar a Pro — $15/mes",
+    "ctaSeePlans": "Ver planes",
+    "ctaWait": "Esperar al reinicio"
   }
 }

frontend/src/i18n/locales/pt-br/common.json

@@ -402,5 +402,17 @@
         "failed": "Falha no registro."
       }
     }
+  },
+  "quotaModal": {
+    "titleFree": "Você atingiu o limite gratuito de hoje",
+    "titlePaid": "Você atingiu seu limite diário",
+    "bodyFree": "Contas Free recebem {{cap}} mensagens de IA por dia. O Pro ($15/mês) te dá {{proCap}}/dia — {{multiplier}}× o limite. Ou espere até sua cota reiniciar.",
+    "bodyPaid": "Seu plano {{plan}} permite {{cap}} mensagens por dia. Faça upgrade ou aguarde o reinício.",
+    "today": "Hoje",
+    "thisMonth": "Este mês",
+    "resets": "Reinicia",
+    "ctaUpgrade": "Fazer upgrade para Pro — $15/mês",
+    "ctaSeePlans": "Ver planos",
+    "ctaWait": "Aguardar reinício"
   }
 }

frontend/src/i18n/locales/zh-cn/common.json

@@ -402,5 +402,17 @@
         "failed": "注册失败。"
       }
     }
+  },
+  "quotaModal": {
+    "titleFree": "今日免费额度已用完",
+    "titlePaid": "已达到每日上限",
+    "bodyFree": "免费账户每天有 {{cap}} 条 AI 消息。Pro ($15/月) 可享 {{proCap}}/天 —— 是免费版的 {{multiplier}} 倍。或等待配额重置。",
+    "bodyPaid": "您的 {{plan}} 套餐每天允许 {{cap}} 条消息。升级到更高级别或等待重置。",
+    "today": "今日",
+    "thisMonth": "本月",
+    "resets": "重置时间",
+    "ctaUpgrade": "升级到 Pro — $15/月",
+    "ctaSeePlans": "查看套餐",
+    "ctaWait": "等待重置"
   }
 }