fix: place cursor at beginning of text field when quoting a note

When a user hits Quote, the new post screen opens with the nostr URI
pre-filled but the cursor was at the end (after the URI). This moves
the cursor to the beginning so the user can immediately start typing
their commentary.

https://claude.ai/code/session_01RPseKC9GJ8hs3GGBR85ezw

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/compose/TextFieldStateExtensions.kt

@@ -25,6 +25,13 @@ import androidx.compose.ui.text.TextRange
 import kotlin.math.max
 import kotlin.math.min
 
+fun TextFieldState.setTextAndPlaceCursorAtBeginning(text: String) {
+    edit {
+        replace(0, length, text)
+        selection = TextRange(0, 0)
+    }
+}
+
 fun TextFieldState.insertUrlAtCursor(url: String) {
     edit {
         var toInsert = url.trim()