fix(voice): say the quadrant is missing instead of "could not be read"

"ترمیم برای دندون دو" set the treatment type but reported the tooth as
unreadable. Nothing was misheard: position 2 arrived intact, with no
quadrant, because none was spoken — four teeth carry position 2 and the
resolver correctly refused to pick one. Only the label was wrong, and it
sent the clinician looking for a transcription fault.

Adds a tooth_missing_quadrant reason that names what is missing and shows
how to say it ("دو بالا راست"), and tells the model explicitly to report a
quadrant-less number with arch and side null rather than guessing.

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

frontend/src/types/voice.ts

@@ -5,6 +5,7 @@ import type { FdiToothId, ToothSelectionGroup } from '@/types/treatment';
 export type VoiceUnresolvedReason =
   | 'not_permanent_tooth'
   | 'position_out_of_range'
+  | 'tooth_missing_quadrant'
   | 'malformed'
   | 'span_not_same_arch'
   | 'unknown_catalog_code'