Add Hardcover shelf sync & unify book mappings

Introduce Hardcover provider support and consolidate per-provider book mapping tables into a unified BookMapping model. Adds two Prisma migrations (add_hardcover_shelves, unify_book_mappings), new backend services (hardcover-api, shelf-sync-core), and provider-specific sync logic and API routes for hardcover shelves with token/list validation. Frontend: new HardcoverForm component, refactor AddShelfModal to support Hardcover, hook updates, and small UI/accessibility tweaks. Also add documentation for Goodreads and Hardcover sync flows and update tests to cover scheduler/prisma helpers.

prisma/migrations/20260303200000_add_hardcover_shelves/migration.sql

@@ -0,0 +1,49 @@
+-- CreateTable
+CREATE TABLE "hardcover_shelves" (
+    "id" TEXT NOT NULL,
+    "user_id" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "list_id" TEXT NOT NULL,
+    "api_token" TEXT NOT NULL,
+    "last_sync_at" TIMESTAMP(3),
+    "book_count" INTEGER,
+    "cover_urls" TEXT,
+    "created_at" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updated_at" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "hardcover_shelves_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "hardcover_book_mappings" (
+    "id" TEXT NOT NULL,
+    "hardcover_book_id" TEXT NOT NULL,
+    "title" TEXT NOT NULL,
+    "author" TEXT NOT NULL,
+    "audible_asin" TEXT,
+    "cover_url" TEXT,
+    "no_match" BOOLEAN NOT NULL DEFAULT false,
+    "last_search_at" TIMESTAMP(3),
+    "created_at" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updated_at" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "hardcover_book_mappings_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE INDEX "hardcover_shelves_user_id_idx" ON "hardcover_shelves"("user_id");
+
+-- CreateIndex
+CREATE UNIQUE INDEX "hardcover_shelves_user_id_list_id_key" ON "hardcover_shelves"("user_id", "list_id");
+
+-- CreateIndex
+CREATE UNIQUE INDEX "hardcover_book_mappings_hardcover_book_id_key" ON "hardcover_book_mappings"("hardcover_book_id");
+
+-- CreateIndex
+CREATE INDEX "hardcover_book_mappings_hardcover_book_id_idx" ON "hardcover_book_mappings"("hardcover_book_id");
+
+-- CreateIndex
+CREATE INDEX "hardcover_book_mappings_audible_asin_idx" ON "hardcover_book_mappings"("audible_asin");
+
+-- AddForeignKey
+ALTER TABLE "hardcover_shelves" ADD CONSTRAINT "hardcover_shelves_user_id_fkey" FOREIGN KEY ("user_id") REFERENCES "users"("id") ON DELETE CASCADE ON UPDATE CASCADE;

prisma/migrations/20260304000000_unify_book_mappings/migration.sql

@@ -0,0 +1,41 @@
+-- CreateTable
+CREATE TABLE "book_mappings" (
+    "id" TEXT NOT NULL,
+    "provider" TEXT NOT NULL,
+    "external_book_id" TEXT NOT NULL,
+    "title" TEXT NOT NULL,
+    "author" TEXT NOT NULL,
+    "audible_asin" TEXT,
+    "cover_url" TEXT,
+    "no_match" BOOLEAN NOT NULL DEFAULT false,
+    "last_search_at" TIMESTAMP(3),
+    "created_at" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updated_at" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "book_mappings_pkey" PRIMARY KEY ("id")
+);
+
+-- Migrate data from goodreads_book_mappings
+INSERT INTO "book_mappings" ("id", "provider", "external_book_id", "title", "author", "audible_asin", "cover_url", "no_match", "last_search_at", "created_at", "updated_at")
+SELECT "id", 'goodreads', "goodreads_book_id", "title", "author", "audible_asin", "cover_url", "no_match", "last_search_at", "created_at", "updated_at"
+FROM "goodreads_book_mappings";
+
+-- Migrate data from hardcover_book_mappings
+INSERT INTO "book_mappings" ("id", "provider", "external_book_id", "title", "author", "audible_asin", "cover_url", "no_match", "last_search_at", "created_at", "updated_at")
+SELECT "id", 'hardcover', "hardcover_book_id", "title", "author", "audible_asin", "cover_url", "no_match", "last_search_at", "created_at", "updated_at"
+FROM "hardcover_book_mappings";
+
+-- DropTable
+DROP TABLE "goodreads_book_mappings";
+
+-- DropTable
+DROP TABLE "hardcover_book_mappings";
+
+-- CreateIndex
+CREATE UNIQUE INDEX "book_mappings_provider_external_book_id_key" ON "book_mappings"("provider", "external_book_id");
+
+-- CreateIndex
+CREATE INDEX "book_mappings_provider_external_book_id_idx" ON "book_mappings"("provider", "external_book_id");
+
+-- CreateIndex
+CREATE INDEX "book_mappings_audible_asin_idx" ON "book_mappings"("audible_asin");

prisma/schema.prisma

@@ -518,26 +518,34 @@ model GoodreadsShelf {
   @@map("goodreads_shelves")
 }
 
-model GoodreadsBookMapping {
-  id              String    @id @default(uuid())
-  goodreadsBookId String    @unique @map("goodreads_book_id")
-  title           String
-  author          String
-  audibleAsin     String?   @map("audible_asin")
-  coverUrl        String?   @map("cover_url") @db.Text
-  noMatch         Boolean   @default(false) @map("no_match")
-  lastSearchAt    DateTime? @map("last_search_at")
-  createdAt       DateTime  @default(now()) @map("created_at")
-  updatedAt       DateTime  @updatedAt @map("updated_at")
+// ============================================================================
+// UNIFIED BOOK MAPPING TABLE
+// Global book-to-ASIN mapping cache shared across all shelf providers.
+// Uses provider + externalBookId composite key for cross-provider dedup.
+// ============================================================================
 
-  @@index([goodreadsBookId])
+model BookMapping {
+  id             String    @id @default(uuid())
+  provider       String    // "goodreads", "hardcover", etc.
+  externalBookId String    @map("external_book_id")
+  title          String
+  author         String
+  audibleAsin    String?   @map("audible_asin")
+  coverUrl       String?   @map("cover_url") @db.Text
+  noMatch        Boolean   @default(false) @map("no_match")
+  lastSearchAt   DateTime? @map("last_search_at")
+  createdAt      DateTime  @default(now()) @map("created_at")
+  updatedAt      DateTime  @updatedAt @map("updated_at")
+
+  @@unique([provider, externalBookId])
+  @@index([provider, externalBookId])
   @@index([audibleAsin])
-  @@map("goodreads_book_mappings")
+  @@map("book_mappings")
 }
 
 // ============================================================================
 // HARDCOVER SYNC TABLES
-// Per-user Hardcover list subscriptions + global book-to-ASIN mapping cache
+// Per-user Hardcover list subscriptions
 // ============================================================================
 
 model HardcoverShelf {
@@ -560,23 +568,6 @@ model HardcoverShelf {
   @@map("hardcover_shelves")
 }
 
-model HardcoverBookMapping {
-  id              String    @id @default(uuid())
-  hardcoverBookId String    @unique @map("hardcover_book_id") // Internal ID from Hardcover
-  title           String
-  author          String
-  audibleAsin     String?   @map("audible_asin")
-  coverUrl        String?   @map("cover_url") @db.Text
-  noMatch         Boolean   @default(false) @map("no_match")
-  lastSearchAt    DateTime? @map("last_search_at")
-  createdAt       DateTime  @default(now()) @map("created_at")
-  updatedAt       DateTime  @updatedAt @map("updated_at")
-
-  @@index([hardcoverBookId])
-  @@index([audibleAsin])
-  @@map("hardcover_book_mappings")
-}
-
 // ============================================================================
 // WORKS TABLE
 // Cross-ASIN audiobook identity mapping — links multiple Audible ASINs