feat(schema): ingredient.section_heading (Migration 012 + Type)

Fuegt das nullable Feld section_heading zur ingredient-Tabelle hinzu
(Migration 012), erweitert den Ingredient-Typ und aktualisiert alle drei
Return-Stellen in parseIngredient. Downstream-Sites (repository, Editor,
Tests) bleiben rot – werden in Task 2+ behoben.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/server/db/migrations/012_ingredient_section.sql

@@ -0,0 +1,4 @@
+-- Nullable -- old rows keep NULL, new rows may have a section heading.
+-- Rendering rule: if section_heading is set (not NULL and not empty),
+-- a new section with this title starts at this ingredient row.
+ALTER TABLE ingredient ADD COLUMN section_heading TEXT;

src/lib/server/parsers/ingredient.ts

@@ -105,16 +105,16 @@ export function parseIngredient(raw: string, position = 0): Ingredient {
     if (tail.length > 0) {
       const quantity = clampQuantity(UNICODE_FRACTION_MAP[firstChar]);
       const { unit, name } = splitUnitAndName(tail);
-      return { position, quantity, unit, name, note, raw_text: rawText };
+      return { position, quantity, unit, name, note, raw_text: rawText, section_heading: null };
     }
   }
 
   const qtyPattern = /^((?:\d+[.,]?\d*(?:\s*[-–]\s*\d+[.,]?\d*)?)|(?:\d+\/\d+))\s+(.+)$/;
   const qtyMatch = qtyPattern.exec(working);
   if (!qtyMatch) {
-    return { position, quantity: null, unit: null, name: working, note, raw_text: rawText };
+    return { position, quantity: null, unit: null, name: working, note, raw_text: rawText, section_heading: null };
   }
   const quantity = clampQuantity(parseQuantity(qtyMatch[1]));
   const { unit, name } = splitUnitAndName(qtyMatch[2]);
-  return { position, quantity, unit, name, note, raw_text: rawText };
+  return { position, quantity, unit, name, note, raw_text: rawText, section_heading: null };
 }

src/lib/types.ts

@@ -5,6 +5,7 @@ export type Ingredient = {
   name: string;
   note: string | null;
   raw_text: string;
+  section_heading: string | null;
 };
 
 export type Step = {