feat(gps): klare Fehlerhinweise, Empfangsqualität und Live-Log-Freigabe

Nutzer sehen spezifische Meldungen bei GPS-Problemen, eine Schätzung des
Empfangs aus der Browser-Genauigkeit und beim ersten Live-Log-Besuch nur
dann einen Freigabe-Hinweis, wenn die Standortberechtigung noch offen ist.

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

client/src/i18n/locales/en.json

@@ -381,6 +381,24 @@
       "event_location_placeholder": "e.g. Kiel",
       "event_remarks": "Remarks / Events",
       "gps_btn": "Get GPS Location",
+      "gps_permission_denied": "Location access was denied. Allow it in your browser or device settings and try again.",
+      "gps_timeout": "GPS timed out. Try again outdoors with a clear view of the sky.",
+      "gps_position_unavailable": "No GPS signal available. Wait and retry, or enter coordinates manually.",
+      "gps_unavailable": "GPS is not supported by this browser or device.",
+      "gps_failed": "Could not determine GPS position.",
+      "gps_fallback_no_location": "GPS failed. Enter a place under Location / harbour, departure, or destination, or type coordinates manually.",
+      "gps_fallback_success": "Coordinates for \"{{location}}\" resolved from place name (not GPS).",
+      "gps_fallback_failed": "GPS and place-name lookup both failed. Please enter coordinates manually.",
+      "gps_quality_excellent": "Strong GPS reception (±{{accuracy}} m)",
+      "gps_quality_good": "Good GPS reception (±{{accuracy}} m)",
+      "gps_quality_fair": "Fair GPS reception (±{{accuracy}} m) — move outdoors for a better fix.",
+      "gps_quality_poor": "Weak GPS reception (±{{accuracy}} m) — likely few satellites. Retry outdoors or verify the position.",
+      "gps_quality_unknown": "GPS position applied (accuracy not reported by device).",
+      "gps_live_intro_title": "Location for Live Log",
+      "gps_live_intro_body": "The app needs your location for automatic position entries and the GPS button.\n\nTap “Allow location” and confirm in the next dialog. You can always enter a position manually via “Position”.",
+      "gps_live_intro_allow": "Allow location",
+      "gps_live_intro_later": "Later",
+      "gps_enable_in_settings_hint": "Location access is blocked. You can allow it later in your browser or device settings (site / app → Location).",
       "weather_btn": "Fetch OpenWeatherMap Weather",
       "weather_offline": "OpenWeatherMap requires an internet connection. You are currently offline.",
       "event_wind_pressure": "Barometer (hPa)",