feat(bot): answer treatment questions from the clinical-guideline knowledge base

- menu button «Вопрос о лечении» -> kb.question -> rag.answer (KR quote + source)
  or «уточните у врача»; dose questions get a fixed doctor redirect
- free text in idle that looks like a question (no check-in signals, not a drug
  question) -> knowledge base; no answer -> the usual support phrase
- routing order unchanged: consent/safety first, side effects/quit/alcohol -> check-in,
  own drug -> med_qa (instruction only, SPEC §7 p.5)
- question cues, small talk and texts in config/texts/knowledge.yaml; scrub placeholders
  before "что такое X" no longer hide the definition question

Refs #64

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/dialog/flows/core.py

@@ -39,6 +39,7 @@ def menu_reply(ctx: Ctx, text: str | None = None) -> Reply:
     buttons = [
         [Button(label=b.checkin, data="menu:checkin")],
         [Button(label=b.med_question, data="menu:med_question")],
+        [Button(label=b.kb_question, data="menu:kb_question")],
         [Button(label=b.contact_doctor, data="menu:contact_doctor")],
         [Button(label=b.revoke, data="consent:revoke")],
     ]