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/schemas/planner_config.py

@@ -0,0 +1,57 @@
+from __future__ import annotations
+
+from typing import Optional
+
+from pydantic import BaseModel, Field, model_validator
+
+
+class PlannerConfigOverride(BaseModel):
+    recency_weeks: Optional[int] = Field(default=None, ge=0)
+    calorie_tolerance_pct: Optional[int] = Field(default=None, ge=0, le=100)
+    max_total_minutes: Optional[int] = Field(default=None, ge=0)
+    max_meal_cost: Optional[float] = Field(default=None, ge=0)
+    w_savings: Optional[float] = Field(default=None, ge=0, le=1)
+    w_coverage: Optional[float] = Field(default=None, ge=0, le=1)
+    w_pantry: Optional[float] = Field(default=None, ge=0, le=1)
+    w_time: Optional[float] = Field(default=None, ge=0, le=1)
+    w_recency: Optional[float] = Field(default=None, ge=0, le=1)
+    time_ideal_minutes: Optional[int] = Field(default=None, ge=0)
+    time_full_minutes: Optional[int] = Field(default=None, ge=0)
+    recency_full_weeks: Optional[int] = Field(default=None, ge=0)
+    top_k: Optional[int] = Field(default=None, ge=1)
+    set_size: Optional[int] = Field(default=None, ge=1)
+    p_protein: Optional[float] = Field(default=None, ge=0)
+    p_cuisine: Optional[float] = Field(default=None, ge=0)
+
+    @model_validator(mode="after")
+    def _check_weights_sum(self):
+        weights = [self.w_savings, self.w_coverage, self.w_pantry, self.w_time, self.w_recency]
+        if all(w is not None for w in weights):
+            total = sum(weights)
+            if not 0.999 <= total <= 1.001:
+                raise ValueError(f"weights must sum to 1.0, got {total:.4f}")
+        return self
+
+
+class PlannerConfigResponse(BaseModel):
+    recency_weeks: int
+    calorie_tolerance_pct: int
+    max_total_minutes: int
+    max_meal_cost: float
+    w_savings: float
+    w_coverage: float
+    w_pantry: float
+    w_time: float
+    w_recency: float
+    time_ideal_minutes: int
+    time_full_minutes: int
+    recency_full_weeks: int
+    top_k: int
+    set_size: int
+    p_protein: float
+    p_cuisine: float
+    source: str = "default"
+
+
+class PlannerConfigUpdateRequest(BaseModel):
+    planner_config: PlannerConfigOverride