fix(dashboard): Rasterversion schuetzen, Kalender-Mindestbreite, Breiten je Breakpoint, Hintergrund

- Layout mit neuerer Rasterversion wird nie gespeichert, Bearbeiten gesperrt mit Hinweis
- Kalender minW 11 (~260 px bei lg), Breiten je Breakpoint auf Spaltenzahl begrenzt
- optimistische Ruecksetzung nur, wenn noch der gesetzte Wert steht
- Titel-Schalter mit fester Beschriftung + aria-pressed
- Hintergrund-Dialog: Fokus rein/zurueck, Tab bleibt im Dialog
- Loeschen eines Bildes setzt eine darauf zeigende Hintergrund-Wahl zurueck
- Uebersetzungen und CHANGELOG

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

apps/web/src/messages/en.json

@@ -246,7 +246,6 @@
     "catalogClose": "Close dialog",
     "deleteTooltip": "Remove widget",
     "hideTitle": "Hide title",
-    "showTitle": "Show title",
     "dragHint": "Drag the tile to move it",
     "editMode": "Edit dashboard",
     "saveChanges": "Save changes",
@@ -498,6 +497,7 @@
       "snooze10m": "In 10 minutes",
       "snooze1h": "In 1 hour",
       "snoozeTomorrow": "Tomorrow at {time}",
+      "snoozeToday": "Today at {time}",
       "edit": "Edit reminder",
       "editTitle": "Edit reminder",
       "delete": "Delete reminder",
@@ -515,6 +515,7 @@
     },
     "editShort": "Edit",
     "done": "Done",
+    "reloadRequired": "This dashboard was saved by a newer version of Tessera. Please reload the page to edit it.",
     "toolbarLabel": "Dashboard actions",
     "emptyState": {
       "title": "Your dashboard is still empty",
@@ -1402,6 +1403,7 @@
   "customModules": {
     "openInNewTab": "Open in new tab",
     "notFound": "This module no longer exists.",
+    "loadError": "This module could not be loaded. Please try again later.",
     "invalidUrl": "This module's address is not a valid https address and is therefore not shown.",
     "loading": "Loading …",
     "form": {
@@ -1416,6 +1418,8 @@
       "urlCredentials": "The address must not contain a user name or a password.",
       "saveError": "The module could not be saved. Please try again.",
       "deleteError": "The module could not be deleted. Please try again.",
+      "forbidden": "You do not have permission for this action.",
+      "invalidInput": "The details were not accepted. Please check name, address and category.",
       "deleteConfirm": {
         "title": "Delete custom module",
         "bodyShared": "Do you really want to delete “{name}”? The entry disappears from the sidebar for all users.",