Show clear offline messages for OWM weather and AI summaries.

Users see localized feedback when OpenWeatherMap or travel-day summary
features are used without connectivity, instead of generic API errors.

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

client/src/i18n/locales/en.json

@@ -358,6 +358,7 @@
       "event_remarks": "Remarks / Events",
       "gps_btn": "Get GPS Location",
       "weather_btn": "Fetch OpenWeatherMap Weather",
+      "weather_offline": "OpenWeatherMap requires an internet connection. You are currently offline.",
       "event_wind_pressure": "Barometer (hPa)",
       "event_heel": "Heel Angle (°)",
       "event_sails": "Sails / Motor Status",
@@ -381,6 +382,7 @@
       "ai_summary_error_no_key": "No OpenRouter API key configured on the server.",
       "ai_summary_error_rate_limited": "Maximum number of generations reached for this travel day.",
       "ai_summary_error_forbidden": "Only the skipper may generate AI summaries.",
+      "ai_summary_offline": "AI summary generation requires an internet connection. You are currently offline.",
       "photos_title": "Photo Attachments (E2E Encrypted)",
       "photo_caption_label": "Photo Caption / Label (Optional)",
       "photo_caption_placeholder": "e.g. Setting sails near harbor entrance",