fix(server): support nested subfolders in book dock discovery

Recurse into nested subfolders during book dock watcher scans and discovery so that books organized under category or author subdirectories are processed. Keep shared folders from claiming exclusive directory ownership so siblings and multi-track units can finalize and discard cleanly without collisions.

Closes #1311

server/test/book-dock-ingest-finalize.e2e-spec.ts

@@ -1,4 +1,4 @@
-import { mkdir, readFile, writeFile } from 'fs/promises';
+import { mkdir, readFile, realpath, utimes, writeFile } from 'fs/promises';
 import { dirname, join } from 'path';
 import { afterEach } from 'vitest';
 
@@ -310,6 +310,69 @@ describe('Book Dock ingest + finalize (e2e)', () => {
     expect(await fileExists(untouched.absolutePath)).toBe(true);
   });
 
+  it.each(['finalize', 'discard'] as const)('rescans nested shared-folder books and %ss only the selected book', async (action) => {
+    const destination = await createLibraryWithFolder(context);
+    const dock = await realpath(context.fixture.bookDockPath);
+    const directory = join(dock, 'ebooks', 'Author', 'Title');
+    await mkdir(directory, { recursive: true });
+    const firstPath = join(directory, 'first.fb2');
+    const old = new Date(Date.now() - 120_000);
+    await writeFile(firstPath, buildFb2Fixture({ title: 'First Nested Book' }));
+    await utimes(firstPath, old, old);
+
+    const rescan = () => context.app.inject({ method: 'POST', url: '/api/v1/book-dock/rescan', headers: authHeader(context.adminToken) });
+    expect((await rescan()).statusCode).toBe(204);
+    const [first] = await context.db.select().from(schema.bookDockFiles).where(eq(schema.bookDockFiles.absolutePath, firstPath));
+    expect(first?.unitDirectory).toBe(directory);
+    await waitForBookDockStatus(context, first.id, ['ready']);
+
+    const secondPath = join(directory, 'second.fb2');
+    await writeFile(secondPath, buildFb2Fixture({ title: 'Second Nested Book' }));
+    const pdfPath = await createPdfFixture(directory, 'second.pdf', 'Second Nested Book');
+    await utimes(secondPath, old, old);
+    await utimes(pdfPath, old, old);
+    expect((await rescan()).statusCode).toBe(204);
+    expect((await rescan()).statusCode).toBe(204);
+    const dockRows = await context.db.select().from(schema.bookDockFiles);
+    expect(dockRows).toHaveLength(2);
+    const second = dockRows.find((row) => row.absolutePath === secondPath)!;
+    expect(second.unitDirectory).toBeNull();
+    await waitForBookDockStatus(context, second.id, ['ready']);
+
+    const detail = await context.app.inject({ method: 'GET', url: `/api/v1/book-dock/files/${second.id}`, headers: authHeader(context.adminToken) });
+    expect(detail.statusCode).toBe(200);
+    expect((detail.json() as BookDockFile).unitFiles.map((file) => file.fileName).sort()).toEqual(['second.fb2', 'second.pdf']);
+
+    if (action === 'finalize') {
+      const response = await context.app.inject({
+        method: 'POST',
+        url: '/api/v1/book-dock/finalize',
+        headers: authHeader(context.adminToken),
+        payload: { fileIds: [second.id], defaultLibraryId: destination.libraryId, defaultFolderId: destination.libraryFolderId },
+      });
+      expect(response.statusCode).toBe(201);
+      const result = response.json() as BookDockFinalizeResult;
+      expect(result).toMatchObject({ total: 1, succeeded: 1, failed: 0 });
+      const files = await context.db.select().from(schema.bookFiles).where(eq(schema.bookFiles.bookId, result.results[0].bookId!));
+      expect(files.map((file) => file.format).sort()).toEqual(['fb2', 'pdf']);
+      expect(new Set(files.map((file) => dirname(file.absolutePath))).size).toBe(1);
+      for (const file of files) expect(await fileExists(file.absolutePath)).toBe(true);
+    } else {
+      const response = await context.app.inject({
+        method: 'DELETE',
+        url: `/api/v1/book-dock/files/${second.id}`,
+        headers: authHeader(context.adminToken),
+      });
+      expect(response.statusCode).toBe(204);
+    }
+
+    expect(await fileExists(firstPath)).toBe(true);
+    expect(await getBookDockRow(context, first.id)).toBeDefined();
+    expect(await fileExists(secondPath)).toBe(false);
+    expect(await fileExists(pdfPath)).toBe(false);
+    expect(await getBookDockRow(context, second.id)).toBeUndefined();
+  });
+
   it('finalize moves files into destination and creates book records', async () => {
     const destination = await createLibraryWithFolder(context);
     const bookDockRow = await createBookDockRow(context, {

server/test/e2e.setup.ts

@@ -1,5 +1,6 @@
 import { vi } from 'vitest';
 
-vi.mock('../src/modules/scanner/lib/stability', () => ({
+vi.mock('../src/modules/scanner/lib/stability', async (importOriginal) => ({
+  ...(await importOriginal<typeof import('../src/modules/scanner/lib/stability')>()),
   waitForStability: vi.fn().mockResolvedValue(undefined),
 }));