feat(sharing): let share recipients recolour a shared calendar

The colour dot for a shared (non-owned) local calendar was disabled, and the
colour write hit the owner-only PUT /calendars/{id} (404 for recipients). Now
the dot is always editable and colour changes go through the dedicated
PUT /calendars/{id}/color endpoint, which stores a recipient's own per-user
colour server-side (synced across devices) without granting write or rename.
Renaming stays owner-only (no rename UI for shared calendars).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/java/com/scarriffle/calendarr/data/CalendarRepository.kt

@@ -222,9 +222,11 @@ class CalendarRepository @Inject constructor(
     suspend fun deleteHomeAssistantAccount(id: Int) =
         guarded { api.deleteHomeAssistantAccount(id).ensureSuccess() }
 
-    /** Change a local calendar's colour. */
+    /** Change a local calendar's colour. Uses the colour-only endpoint so share
+     *  recipients can recolour their view (own per-user colour) without needing
+     *  write access or being able to rename the calendar. */
     suspend fun updateLocalCalendarColor(id: Int, color: String) = guarded {
-        api.updateLocalCalendar(id, jsonBody("color" to color)).ensureSuccess()
+        api.setLocalCalendarColor(id, jsonBody("color" to color)).ensureSuccess()
     }
 
     /** Change an iCal subscription's colour. */

app/src/main/java/com/scarriffle/calendarr/data/remote/CalendarrApi.kt

@@ -155,6 +155,11 @@ interface CalendarrApi {
     @PUT("api/local/calendars/{id}")
     suspend fun updateLocalCalendar(@Path("id") id: Int, @Body body: RequestBody): Response<ResponseBody>
 
+    // Colour-only update that works for owners AND share recipients (recipients
+    // get their own per-user colour; owners change the calendar's colour).
+    @PUT("api/local/calendars/{id}/color")
+    suspend fun setLocalCalendarColor(@Path("id") id: Int, @Body body: RequestBody): Response<ResponseBody>
+
     @DELETE("api/local/calendars/{id}")
     suspend fun deleteLocalCalendar(@Path("id") id: Int): Response<ResponseBody>
 

app/src/main/java/com/scarriffle/calendarr/ui/accounts/AccountsScreen.kt

@@ -380,7 +380,9 @@ private fun LocalCalendarRow(
 ) {
     var menu by remember { mutableStateOf(false) }
     Row(Modifier.fillMaxWidth().padding(vertical = 6.dp), verticalAlignment = Alignment.CenterVertically) {
-        ColorDot(cal.color, editable = cal.owned, onClick = onColor)
+        // Recipients of a shared calendar may recolour it (their own per-user
+        // colour); only renaming/other management stays owner-only.
+        ColorDot(cal.color, editable = true, onClick = onColor)
         Column(Modifier.weight(1f).padding(start = 12.dp)) {
             Row(verticalAlignment = Alignment.CenterVertically) {
                 Text(cal.name, style = MaterialTheme.typography.bodyLarge)