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/ai/kettlebell.py

@@ -55,3 +55,47 @@ class KettlebellModule(dspy.Module):
 
 
 kettlebell_module = KettlebellModule()
+
+
+class RefineKettlebellSession(dspy.Signature):
+    """Refine an existing kettlebell workout session based on user feedback.
+
+    You are given the current session and the user's feedback. Apply the requested changes
+    while keeping the rest of the session intact. Maintain proper exercise sequencing,
+    warm-up/cooldown structure, and ensure total work time still fits the target duration.
+    """
+
+    current_session: str = dspy.InputField(desc="JSON representation of the current session")
+    user_feedback: str = dspy.InputField(desc="User's requested changes to the session")
+    user_profile: str = dspy.InputField(desc="User details including age, weight, fitness level, and goals")
+    available_weights_kg: str = dspy.InputField(desc="Comma-separated list of available kettlebell weights in kg")
+    focus: str = dspy.InputField(desc="Session focus: strength, conditioning, mobility, fat loss, etc.")
+    duration_minutes: int = dspy.InputField(desc="Target session duration in minutes")
+    session: KettlebellSessionOutput = dspy.OutputField(desc="Refined structured kettlebell session")
+
+
+class KettlebellRefineModule(dspy.Module):
+    def __init__(self):
+        super().__init__()
+        self.refine = dspy.ChainOfThought(RefineKettlebellSession)
+
+    def forward(
+        self,
+        current_session: str,
+        user_feedback: str,
+        user_profile: str,
+        available_weights_kg: str,
+        focus: str,
+        duration_minutes: int,
+    ):
+        return self.refine(
+            current_session=current_session,
+            user_feedback=user_feedback,
+            user_profile=user_profile,
+            available_weights_kg=available_weights_kg,
+            focus=focus,
+            duration_minutes=duration_minutes,
+        )
+
+
+kettlebell_refine_module = KettlebellRefineModule()