feat(ai): Vercel AI SDK provider factory with BYOK and per-use-case model prefs

Provider factory (OpenAI/Anthropic/OpenRouter/Ollama). generateObject for all outputs.
Features: recipe generation, photo-to-recipe vision, variations, drink/meal pairings,
ingredient substitution, recipe adaptation, nutrition analysis, URL import, meal plan gen.
User BYOK keys (AES-256-GCM). Per-use-case model preferences (text/vision/mealPlan).
Site-level key override via admin settings.

apps/web/lib/ai/features/infer-dietary.ts

@@ -0,0 +1,36 @@
+import { generateObject } from "ai";
+import { z } from "zod";
+import { resolveModel, type AiConfig } from "../factory";
+
+const DietaryOutputSchema = z.object({
+  vegan: z.boolean(),
+  vegetarian: z.boolean(),
+  glutenFree: z.boolean(),
+  dairyFree: z.boolean(),
+  nutFree: z.boolean(),
+  halal: z.boolean(),
+  kosher: z.boolean(),
+  reasoning: z.record(z.string(), z.string()).optional(),
+});
+
+export type InferredDietaryTags = Omit<z.infer<typeof DietaryOutputSchema>, "reasoning">;
+
+export async function inferDietaryTags(
+  ingredients: Array<{ rawName: string; unit?: string | null }>,
+  config?: AiConfig
+): Promise<InferredDietaryTags> {
+  const model = resolveModel(config);
+
+  const ingredientList = ingredients.map((i) => i.rawName).join(", ");
+
+  const { object } = await generateObject({
+    model,
+    schema: DietaryOutputSchema,
+    system:
+      "You are a dietary classification expert. Analyze recipe ingredients and determine dietary tags accurately. Be conservative — only mark something as true if you are confident based on the ingredients listed.",
+    prompt: `Classify these ingredients for dietary tags: ${ingredientList}`,
+  });
+
+  const { reasoning: _reasoning, ...tags } = object;
+  return tags;
+}