Add interactive routine wizard, slider controls, value persistence, and timer pause

- Interactive routine generation wizard with AI refinement loop (generate-draft,
  refine, save-draft endpoints + RoutineWizard modal component)
- Replace +/- stepper buttons with slider controls for reps/weight during workout
- Persist user-modified reps/weight across sets of the same exercise
- Add pause/resume by tapping timer dials, with back-button confirmation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/api/v1/endpoints/kettlebell.py

@@ -1,3 +1,4 @@
+import json
 from collections import defaultdict
 from datetime import datetime, timedelta
 from typing import Any, Dict, List, Optional
@@ -6,7 +7,7 @@ from fastapi import APIRouter, Depends, HTTPException
 from pydantic import BaseModel
 from sqlmodel import Session, select
 
-from app.ai.kettlebell import kettlebell_module
+from app.ai.kettlebell import kettlebell_module, kettlebell_refine_module
 from app.api import deps
 from app.models.kettlebell import KettlebellSession, KettlebellSetLog
 
@@ -19,6 +20,39 @@ class KettlebellGenerateRequest(BaseModel):
     available_weights: list[float]
 
 
+class DraftExercise(BaseModel):
+    order: int
+    name: str
+    description: str
+    sets: int
+    reps: int
+    duration_seconds: int
+    weight_kg: float
+    rest_seconds: int
+    coaching_tip: str
+
+
+class DraftSession(BaseModel):
+    title: str
+    focus: str
+    total_duration_min: int
+    difficulty: str
+    exercises: list[DraftExercise]
+    notes: str
+
+
+class RefineRequest(BaseModel):
+    draft: DraftSession
+    feedback: str
+    focus: str
+    duration_minutes: int
+    available_weights: list[float]
+
+
+class SaveDraftRequest(BaseModel):
+    draft: DraftSession
+
+
 class LogSetRequest(BaseModel):
     exercise_order: int
     set_number: int
@@ -178,6 +212,102 @@ def get_analytics(
     )
 
 
+@router.post("/generate-draft", response_model=DraftSession)
+def generate_draft(
+    *,
+    current_user: deps.CurrentUser,
+    request: KettlebellGenerateRequest,
+) -> Any:
+    """Generate a draft kettlebell session (not saved to DB) for review."""
+    try:
+        user_profile = (
+            f"Age: {current_user.age or 'unknown'}, "
+            f"Gender: {current_user.gender or 'unknown'}, "
+            f"Weight: {current_user.weight or 'unknown'} kg, "
+            f"Height: {current_user.height or 'unknown'} cm"
+        )
+        available_weights_kg = ", ".join(str(w) for w in sorted(request.available_weights))
+        generated = kettlebell_module(
+            user_profile=user_profile,
+            available_weights_kg=available_weights_kg,
+            focus=request.focus,
+            duration_minutes=request.duration_minutes,
+        )
+        s = generated.session
+        return DraftSession(
+            title=s.title,
+            focus=s.focus,
+            total_duration_min=s.total_duration_min,
+            difficulty=s.difficulty,
+            exercises=[DraftExercise(**ex.model_dump()) for ex in s.exercises],
+            notes=s.notes,
+        )
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=str(e))
+
+
+@router.post("/refine", response_model=DraftSession)
+def refine_draft(
+    *,
+    current_user: deps.CurrentUser,
+    request: RefineRequest,
+) -> Any:
+    """Refine a draft session based on user feedback."""
+    try:
+        user_profile = (
+            f"Age: {current_user.age or 'unknown'}, "
+            f"Gender: {current_user.gender or 'unknown'}, "
+            f"Weight: {current_user.weight or 'unknown'} kg, "
+            f"Height: {current_user.height or 'unknown'} cm"
+        )
+        available_weights_kg = ", ".join(str(w) for w in sorted(request.available_weights))
+        current_session_json = json.dumps(request.draft.model_dump(), indent=2)
+        generated = kettlebell_refine_module(
+            current_session=current_session_json,
+            user_feedback=request.feedback,
+            user_profile=user_profile,
+            available_weights_kg=available_weights_kg,
+            focus=request.focus,
+            duration_minutes=request.duration_minutes,
+        )
+        s = generated.session
+        return DraftSession(
+            title=s.title,
+            focus=s.focus,
+            total_duration_min=s.total_duration_min,
+            difficulty=s.difficulty,
+            exercises=[DraftExercise(**ex.model_dump()) for ex in s.exercises],
+            notes=s.notes,
+        )
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=str(e))
+
+
+@router.post("/save-draft", response_model=KettlebellSession)
+def save_draft(
+    *,
+    current_user: deps.CurrentUser,
+    request: SaveDraftRequest,
+    session: Session = Depends(deps.get_session),
+) -> Any:
+    """Save a finalized draft as a new session."""
+    draft = request.draft
+    kb_session = KettlebellSession(
+        user_id=current_user.id,
+        title=draft.title,
+        focus=draft.focus,
+        exercises={"exercises": [ex.model_dump() for ex in draft.exercises]},
+        total_duration_min=draft.total_duration_min,
+        difficulty=draft.difficulty,
+        notes=draft.notes,
+        status="generated",
+    )
+    session.add(kb_session)
+    session.commit()
+    session.refresh(kb_session)
+    return kb_session
+
+
 @router.post("/generate", response_model=KettlebellSession)
 def generate_session(
     *,