feat(diet): lagg till nordisk/carnivore/paleo + LCHF som matvanor med mjuk rankning

- DIET_PATTERNS: +nordic, +carnivore, +paleo (migration 0029). Ingen separat
  "lchf" - LCHF tacks av befintliga "low_carb" for att undvika dubblett med
  keto/low_carb. UI visar low_carb med etiketten "LCHF".
- Mobil onboarding + profil: 9 rena val (allatare..carnivore), 12 sprak.
- recommendation-engine: ny mjuk dietAffinity-poangterm (0-1, neutral 0.5).
  Rankar recept mot matvanan - ALDRIG hart filter (uteslutande matvanor,
  religion, allergener hanteras redan deterministiskt i sakerhetsfiltret).
  low_carb/keto: lag kolhydrat. carnivore: hog protein + lag kolhydrat.
  paleo: glutenfri/laktosfri-proxyer. nordic: svenskt/nordiskt kok + sasong.
- 6 nya tester (35 grona). Full typecheck 20/20 + mobil gron.

packages/recommendation-engine/test/engine.test.ts

@@ -486,3 +486,72 @@ describe("S4 rekommendationsvyer", () => {
     expect(tasteWeights.taste).toBe(TASTE_VIEW_WEIGHTS.taste);
   });
 });
+
+describe("diet-affinitet (spec §diet, mjuk rankning)", () => {
+  it("utan matvana är affiniteten neutral (0.5)", () => {
+    const scored = scoreCandidate(candidate(), ctx);
+    expect(scored.parts.dietAffinity).toBe(0.5);
+  });
+
+  it("low_carb/LCHF premierar låg kolhydrat", () => {
+    const low = scoreCandidate(candidate({ nutritionPerPortion: { ...nutrition, carbsG: 10 } }), {
+      ...ctx,
+      dietPattern: "low_carb",
+    });
+    const high = scoreCandidate(candidate({ nutritionPerPortion: { ...nutrition, carbsG: 60 } }), {
+      ...ctx,
+      dietPattern: "low_carb",
+    });
+    expect(low.parts.dietAffinity).toBe(1);
+    expect(high.parts.dietAffinity).toBe(0.15);
+  });
+
+  it("explicit low_carb-tagg räcker oavsett makro", () => {
+    const tagged = scoreCandidate(
+      candidate({ tags: ["low_carb"], nutritionPerPortion: { ...nutrition, carbsG: 55 } }),
+      { ...ctx, dietPattern: "keto" },
+    );
+    expect(tagged.parts.dietAffinity).toBe(1);
+  });
+
+  it("carnivore premierar högt protein + låg kolhydrat", () => {
+    const meaty = scoreCandidate(
+      candidate({ nutritionPerPortion: { ...nutrition, proteinG: 45, carbsG: 5 } }),
+      { ...ctx, dietPattern: "carnivore" },
+    );
+    const carby = scoreCandidate(
+      candidate({ nutritionPerPortion: { ...nutrition, proteinG: 12, carbsG: 70 } }),
+      { ...ctx, dietPattern: "carnivore" },
+    );
+    expect(meaty.parts.dietAffinity).toBe(1);
+    expect(meaty.parts.dietAffinity).toBeGreaterThan(carby.parts.dietAffinity ?? 0);
+  });
+
+  it("nordisk premierar svenskt/nordiskt kök", () => {
+    const swedish = scoreCandidate(candidate({ cuisine: "swedish" }), {
+      ...ctx,
+      dietPattern: "nordic",
+    });
+    const italian = scoreCandidate(candidate({ cuisine: "italian" }), {
+      ...ctx,
+      dietPattern: "nordic",
+    });
+    expect(swedish.parts.dietAffinity).toBe(0.85);
+    expect(swedish.parts.dietAffinity).toBeGreaterThan(italian.parts.dietAffinity ?? 0);
+  });
+
+  it("är mjuk rankning, inte hårt filter – ej matchande recept finns kvar", () => {
+    const lowCarbRecipe = candidate({
+      recipeId: "lowcarb",
+      nutritionPerPortion: { ...nutrition, carbsG: 8 },
+    });
+    const pastaRecipe = candidate({
+      recipeId: "pasta",
+      nutritionPerPortion: { ...nutrition, carbsG: 80 },
+    });
+    const ranked = rankAll([pastaRecipe, lowCarbRecipe], { ...ctx, dietPattern: "low_carb" });
+    // Båda recepten finns kvar (inget filtreras bort), men lågkolhydrat rankas högre.
+    expect(ranked).toHaveLength(2);
+    expect(ranked[0]?.recipeId).toBe("lowcarb");
+  });
+});