v0.1.32 - Mix Calculator search, ingredient categories, throughput tidy-up

- Mix Calculator: searchable Mix Name picker (mirrors Throughput search)
- Ingredients Editor: add manual Category column; used to order Mix Calculator output
- Mix Calculator: surface formula-only mixes (no product yet) via -mix_id sentinel
- Throughput: remove unused For order / For stock destination controls from composer
- Editor change history: show timestamps in local time (stored UTC) instead of raw UTC

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/app/api/editor.py

@@ -838,6 +838,7 @@ def _serialize_ingredient(material: RawMaterial, usage_count: int) -> dict:
         "kg_per_unit": material.kg_per_unit,
         "status": material.status,
         "rounding_decimals": material.rounding_decimals,
+        "category": material.category,
         "notes": material.notes,
         "cost_per_kg": cost_per_kg,
         "usage_count": usage_count,
@@ -885,6 +886,7 @@ def create_editor_ingredient(
         kg_per_unit=payload.kg_per_unit,
         status=payload.status.strip() or "active",
         rounding_decimals=payload.rounding_decimals,
+        category=(payload.category or "").strip() or None,
         notes=payload.notes,
     )
     db.add(material)
@@ -928,6 +930,8 @@ def update_editor_ingredient(
         updates["supplier"] = (updates["supplier"] or "").strip() or None
     if "unit_of_measure" in updates and updates["unit_of_measure"] is not None:
         updates["unit_of_measure"] = updates["unit_of_measure"].strip()
+    if "category" in updates:
+        updates["category"] = (updates["category"] or "").strip() or None
     before = {field: getattr(material, field) for field in updates}
     for field, value in updates.items():
         setattr(material, field, value)
@@ -941,6 +945,7 @@ def update_editor_ingredient(
             "kg_per_unit": "Kg per unit",
             "status": "Status",
             "rounding_decimals": "Rounding (dp)",
+            "category": "Category",
             "notes": "Notes",
         },
     )