fix(crash): keep event/calendar content out of exception messages

Audit of our own throw sites, since exception messages land verbatim in
the stack trace a crash report carries. Redacts the three that could hold
user content; the rest only carry numeric ids/timestamps (metadata, kept
for debugging):

- create-local-calendar: drop the user-typed calendar name.
- toContentValues unsupported-type: log the value's type, never the value
  (a cell can be an event title/description/location).
- ics export open-failure: log only the Uri scheme, not the full Uri
  (which can embed the user's chosen filename).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarDataSource.kt

@@ -204,7 +204,8 @@ class AndroidCalendarDataSource @Inject constructor(
             putDescription(description)
         }
         val uri = resolver.insert(localCalendarsUri(), values)
-            ?: throw WriteFailedException("create local calendar '$name'")
+            // No calendar name in the message — it can reach a crash report.
+            ?: throw WriteFailedException("create local calendar")
         return ContentUris.parseId(uri)
     }
 
@@ -685,7 +686,8 @@ class AndroidCalendarDataSource @Inject constructor(
                     is String -> cv.put(column, value)
                     is Long -> cv.put(column, value)
                     is Int -> cv.put(column, value)
-                    else -> error("Unsupported value for $column: $value")
+                    // Only the type, never the value — a cell value can be event content.
+                    else -> error("Unsupported value type for column '$column': ${value::class.simpleName}")
                 }
             }
         }

app/src/main/java/de/jeanlucmakiola/calendula/data/ics/IcsExporter.kt

@@ -24,7 +24,8 @@ class IcsExporter @Inject constructor(
     fun writeDocument(uri: Uri, content: String) {
         context.contentResolver.openOutputStream(uri)?.use { out ->
             out.write(content.toByteArray(Charsets.UTF_8))
-        } ?: throw IOException("Could not open $uri for writing")
+            // Only the scheme — the full Uri can embed the user's chosen filename.
+        } ?: throw IOException("Could not open output stream for export (scheme=${uri.scheme})")
     }
 
     /**