feat: custom recipe cover color/icon + mute auto placeholder palette (v0.51.0)

Two changes to the no-photo cover placeholder shipped last version:

1. Muted the gradient palette (100/40-opacity tints instead of solid -200/
   -950 stops) — the original was too saturated next to real cover photos
   in the same grid, per feedback.
2. New coverIcon/coverColor columns on recipes (nullable text, migration
   0048, additive-only) let the author pin a specific color+icon from the
   recipe editor instead of the automatic per-id pick. getRecipePlaceholder
   now checks these first, falling back to the deterministic hash pick when
   unset — existing recipes are unaffected until edited.

Wired coverIcon/coverColor through every explicit-column recipe select
that feeds a grid card (explore trending/recent, search, feed, for-you) —
the relational-query call sites (recipes page, collections, profile pages)
already return all columns and needed no changes.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/lib/openapi.ts

@@ -62,6 +62,8 @@ export function generateOpenApiSpec(): object {
     difficulty: z.enum(["easy", "medium", "hard"]).nullable(),
     prepMins: z.number().int().nullable(), cookMins: z.number().int().nullable(),
     tags: z.array(z.string()), sourceUrl: z.string().nullable(), language: z.string().nullable(),
+    coverIcon: z.string().nullable().describe("Cover placeholder icon key, used when there's no photo. Null falls back to a deterministic pick from the recipe id."),
+    coverColor: z.string().nullable().describe("Cover placeholder gradient key, used when there's no photo. Null falls back to a deterministic pick from the recipe id."),
     isBatchCook: z.boolean(), nutritionData: z.object({ perServing: NutritionInputRef }).nullable(),
     nutritionManual: z.boolean().describe("True if nutritionData was entered by the author rather than AI-estimated."),
     dietaryTags: DietaryTagsRef, aiGenerated: z.boolean(),
@@ -77,6 +79,7 @@ export function generateOpenApiSpec(): object {
     prepMins: z.number().int().nullable(), cookMins: z.number().int().nullable(),
     tags: z.array(z.string()), dietaryTags: DietaryTagsRef, aiGenerated: z.boolean(),
     language: z.string().nullable(), sourceUrl: z.string().nullable(),
+    coverIcon: z.string().nullable(), coverColor: z.string().nullable(),
     isBatchCook: z.boolean(), nutritionData: z.object({ perServing: NutritionInputRef }).nullable(),
     nutritionManual: z.boolean(),
     createdAt: z.string().datetime(), updatedAt: z.string().datetime(),
@@ -113,6 +116,8 @@ export function generateOpenApiSpec(): object {
       key: z.string().min(1).max(500),
       isCover: z.boolean().default(false),
     })).max(20).default([]),
+    coverIcon: z.string().max(50).nullable().optional(),
+    coverColor: z.string().max(50).nullable().optional(),
     isBatchCook: z.boolean().default(false),
     dishes: z.array(z.object({
       name: z.string().min(1).max(100),
@@ -155,6 +160,8 @@ export function generateOpenApiSpec(): object {
       key: z.string().min(1).max(500),
       isCover: z.boolean().default(false),
     })).max(20).optional(),
+    coverIcon: z.string().max(50).nullable().optional(),
+    coverColor: z.string().max(50).nullable().optional(),
     isBatchCook: z.boolean().optional(),
     dishes: z.array(z.object({
       name: z.string().min(1).max(100),