T08b: Frontend Calendar UI (month view, kanban, ICS, resources, sharing)

- 8 calendar components (MonthView, KanbanBoard, AppointmentModal, TaskDetailPanel, IcsControls, ResourceBooking, SharingSettings + API client)

- 2 pages (/calendar, /calendar/kanban) + zustand store

- 17 vitest tests (MonthView 5, KanbanBoard 6, AppointmentModal 6) all passing

- i18n: calendar namespace in en/de (104 lines each, +exportSuccess key)

- TS strict mode pass, npm run build pass

frontend/src/i18n/locales/en.json

@@ -258,5 +258,110 @@
     "minLength": "At least {{count}} characters required.",
     "maxLength": "At most {{count}} characters allowed.",
     "passwordMismatch": "Passwords do not match."
+  },
+  "calendar": {
+    "title": "Calendar",
+    "kanbanTitle": "Task Kanban",
+    "today": "Today",
+    "previousMonth": "Previous month",
+    "nextMonth": "Next month",
+    "monthView": "Month view",
+    "kanbanView": "Kanban",
+    "weekdays": ["Mo", "Tu", "We", "Th", "Fr", "Sa", "Su"],
+    "months": [
+      "January", "February", "March", "April", "May", "June",
+      "July", "August", "September", "October", "November", "December"
+    ],
+    "newAppointment": "New appointment",
+    "editAppointment": "Edit appointment",
+    "appointmentTitle": "Title",
+    "appointmentDescription": "Description",
+    "appointmentLocation": "Location",
+    "appointmentStart": "Start",
+    "appointmentEnd": "End",
+    "appointmentAllDay": "All day",
+    "appointmentPriority": "Priority",
+    "appointmentSubtype": "Type",
+    "appointmentCalendar": "Calendar",
+    "save": "Save",
+    "cancel": "Cancel",
+    "delete": "Delete",
+    "deleteEntryConfirm": "Really delete this entry?",
+    "noCalendars": "No calendars available. Please create one first.",
+    "noEntries": "No entries in this period.",
+    "loading": "Loading...",
+    "errorLoad": "Could not load entries.",
+    "errorSave": "Could not save entry.",
+    "created": "Entry created.",
+    "updated": "Entry updated.",
+    "deleted": "Entry deleted.",
+    "moved": "Entry moved.",
+    "kanban": {
+      "open": "Open",
+      "in_progress": "In Progress",
+      "done": "Done",
+      "cancelled": "Cancelled",
+      "empty": "No tasks in this column.",
+      "noTasks": "No tasks available."
+    },
+    "subtasks": {
+      "title": "Subtasks",
+      "addPlaceholder": "New subtask...",
+      "add": "Add",
+      "empty": "No subtasks yet.",
+      "added": "Subtask created.",
+      "updated": "Subtask updated."
+    },
+    "ics": {
+      "export": "Export ICS",
+      "import": "Import ICS",
+      "importSuccess": "{{count}} entries imported.",
+      "importPartial": "{{count}} imported, {{errors}} errors.",
+      "importFailed": "Import failed.",
+      "exportSuccess": "ICS file downloaded.",
+      "chooseFile": "Choose file",
+      "noCalendar": "Please select a calendar first."
+    },
+    "resources": {
+      "title": "Resource booking",
+      "select": "Select resource",
+      "none": "No resource",
+      "book": "Book resource",
+      "booked": "Resource booked.",
+      "conflict": "Conflict: this resource is already booked for this time range.",
+      "missingTimes": "The appointment needs both start and end time."
+    },
+    "sharing": {
+      "title": "Sharing",
+      "user": "User",
+      "group": "Group",
+      "userPlaceholder": "User ID",
+      "groupPlaceholder": "Group ID",
+      "permission": "Permission",
+      "permissionRead": "Read",
+      "permissionWrite": "Write",
+      "add": "Add",
+      "list": "Shares",
+      "empty": "No shares yet.",
+      "added": "Share added.",
+      "removed": "Share removed.",
+      "remove": "Remove"
+    },
+    "priority": {
+      "low": "Low",
+      "medium": "Medium",
+      "high": "High"
+    },
+    "status": {
+      "open": "Open",
+      "in_progress": "In Progress",
+      "done": "Done",
+      "cancelled": "Cancelled"
+    },
+    "subtype": {
+      "normal": "Normal",
+      "follow_up": "Follow up",
+      "private": "Private"
+    }
   }
 }