Add KDoc to the single-interface feature API modules

Cover the last remaining interfaces across features/announcement, cachecleaner,
call, contentscanner, createroom, knockrequests, lockscreen, rolesandpermissions,
startchat, userprofile and viewfolder, with their members and parameters.

Grouped into one commit rather than eleven near-empty ones, per the AGENTS.md rule
about tiny commits.

This completes every features/* api module.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

features/viewfolder/api/src/main/kotlin/io/element/android/features/viewfolder/api/TextFileViewer.kt

@@ -12,7 +12,16 @@ import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
 import kotlinx.collections.immutable.ImmutableList
 
+/**
+ * Renders the contents of a text file, used by the log viewer in the developer options.
+ */
 fun interface TextFileViewer {
+    /**
+     * Draws the file, one row per line.
+     *
+     * @param lines the already-read contents of the file.
+     * @param modifier layout modifier for the container.
+     */
     @Composable
     fun Render(
         lines: ImmutableList<String>,