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/texts.py

@@ -47,6 +47,7 @@ class AgeGateTexts(_Strict):
 class IdleButtons(_Strict):
     checkin: str
     med_question: str
+    kb_question: str
     contact_doctor: str
     revoke: str