feat: implement meal planning feature with CRUD operations and UI integration

backend/prisma/migrations/20260416100000_add_meal_plan/migration.sql

@@ -0,0 +1,15 @@
+-- CreateTable
+CREATE TABLE `MealPlanEntry` (
+    `id` INTEGER NOT NULL AUTO_INCREMENT,
+    `date` DATE NOT NULL,
+    `recipeId` INTEGER NOT NULL,
+    `createdAt` DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
+    `updatedAt` DATETIME(3) NOT NULL,
+
+    UNIQUE INDEX `MealPlanEntry_date_key`(`date`),
+    INDEX `MealPlanEntry_date_idx`(`date`),
+    PRIMARY KEY (`id`)
+) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
+
+-- AddForeignKey
+ALTER TABLE `MealPlanEntry` ADD CONSTRAINT `MealPlanEntry_recipeId_fkey` FOREIGN KEY (`recipeId`) REFERENCES `Recipe`(`id`) ON DELETE CASCADE ON UPDATE CASCADE;