fix(voice): repair the two defects the correctness critic found

Both found by the /orchestrate correctness critic against 15ddb9a, and both
verified by hand before fixing.

1. A picked tooth chip was dropped on Apply. pickCandidate ticked the teeth
   row from `available`, which is memoised from `effective` — the value the
   same handler is in the middle of changing. On "ترمیم برای دندون دو" the
   backend returns no teeth, so `available.teeth` was false at pick time and
   `prev.teeth` was false too; `false || false` stuck permanently. A variant
   of the original live-test failure. Each branch now ticks the row it feeds
   and returns, so nothing reads the stale memo.

2. Decision 41's type-row lock was missing. The treatmentType row was a plain
   toggle, and applyVoiceResult derived `labDependent` from
   `result.treatmentType` rather than the `detail.treatmentType` it writes —
   so unticking the type row saved prosthesis lab rows on whatever type the
   appointment purpose had seeded. Row gains a `locked` state, the type row
   locks while the prosthesis row is ticked, Apply sends the forced tick, and
   `labDependent` now comes from the detail being written.

Gates: backend 16 suites / 209 tests, frontend 37 Vitest tests,
tsc --noEmit clean, next build clean, ESLint 0 new warnings
(VoiceReviewSheet.tsx 0 issues; the 10 in TreatmentWorkspace.tsx are
pre-existing and unchanged in count).

Not covered by a test: both fixes live in component state logic, which the
chosen Vitest scope — pure helpers, no React, no DOM — cannot reach. §12's
manual checks cover them.

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

frontend/messages/en.json

@@ -930,6 +930,7 @@
     "voiceNotUnderstood": "Not understood",
     "voicePickTooth": "Which tooth?",
     "voicePickJaw": "Which jaw?",
+    "voiceTypeForcedByProsthesis": "Prosthesis work sets this type — it cannot be unticked.",
     "voiceTeethAndProsthesis": "Teeth and prosthesis",
     "voiceNoProsthesisHeard": "no prosthesis heard",
     "voiceStackRefused": "not added — cannot be combined",