feat(backend): tunable planner weights via family profile config

- Add planner_config JSONB to family_profile model + migration
- Add PlannerConfig.merge(overrides) + to_dict() for family-level override merging
- generate_meal_plan merges family.planner_config into DEFAULT before filtering/scoring/selection
- New endpoints on /api/profile:
  - GET /planner-config — returns merged effective config
  - PUT /planner-config — partial override validation + merge
  - DELETE /planner-config — reset to system defaults
- Schemas: PlannerConfigOverride, PlannerConfigResponse, PlannerConfigUpdateRequest
  with weight-sum validation (0.999–1.001)
- Export RecipeBase/Create/Read/Update from schemas/__init__ to resolve forward refs

backend/app/services/planner/config.py

@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 from dataclasses import dataclass
+from typing import Any
 
 
 @dataclass(frozen=True)
@@ -37,6 +38,53 @@ class PlannerConfig:
         if abs(total - 1.0) > 1e-6:
             raise ValueError(f"weights must sum to 1.0, got {total}")
 
+    def merge(self, overrides: "dict[str, Any]") -> "PlannerConfig":
+        """Return a new PlannerConfig with overrides applied."""
+        current = {
+            "recency_weeks": self.recency_weeks,
+            "calorie_tolerance_pct": self.calorie_tolerance_pct,
+            "max_total_minutes": self.max_total_minutes,
+            "max_meal_cost": self.max_meal_cost,
+            "w_savings": self.w_savings,
+            "w_coverage": self.w_coverage,
+            "w_pantry": self.w_pantry,
+            "w_time": self.w_time,
+            "w_recency": self.w_recency,
+            "time_ideal_minutes": self.time_ideal_minutes,
+            "time_full_minutes": self.time_full_minutes,
+            "recency_full_weeks": self.recency_full_weeks,
+            "top_k": self.top_k,
+            "set_size": self.set_size,
+            "p_protein": self.p_protein,
+            "p_cuisine": self.p_cuisine,
+        }
+        for key, value in overrides.items():
+            if key in current:
+                current[key] = value
+        inst = PlannerConfig(**current)
+        inst.validate()
+        return inst
+
+    def to_dict(self) -> dict[str, Any]:
+        return {
+            "recency_weeks": self.recency_weeks,
+            "calorie_tolerance_pct": self.calorie_tolerance_pct,
+            "max_total_minutes": self.max_total_minutes,
+            "max_meal_cost": self.max_meal_cost,
+            "w_savings": self.w_savings,
+            "w_coverage": self.w_coverage,
+            "w_pantry": self.w_pantry,
+            "w_time": self.w_time,
+            "w_recency": self.w_recency,
+            "time_ideal_minutes": self.time_ideal_minutes,
+            "time_full_minutes": self.time_full_minutes,
+            "recency_full_weeks": self.recency_full_weeks,
+            "top_k": self.top_k,
+            "set_size": self.set_size,
+            "p_protein": self.p_protein,
+            "p_cuisine": self.p_cuisine,
+        }
+
 
 DEFAULT = PlannerConfig()
 DEFAULT.validate()