feat(ebooks): add ISBN normalization and graceful library requirement handling

- Increase ISBN column from VARCHAR(13) to VARCHAR(17) to support ISBN-13 with hyphens
- Add normalize_isbn() database function to automatically remove hyphens and spaces
- Create trigger to auto-normalize ISBNs on INSERT/UPDATE operations
- Update all Ebook and MediaItem queries to use ISBN normalization
- Add GetEbookLibraryID query to check for existing ebook libraries
- Add graceful error handling when no ebook library exists
- Return helpful error message: 'no ebook library found. Please create an ebook library first'
- Create comprehensive tests for ISBN normalization and library selection
- Add Bruno test files for various ISBN formats and error scenarios
- Update documentation with ISBN normalization details

bruno/ebooks/Create Ebook - ISBN with spaces.bru

@@ -0,0 +1,36 @@
+meta {
+  name: Create Ebook with ISBN (with spaces)
+  type: http
+  seq: 10
+}
+
+post {
+  url: {{base_url}}/api/ebooks
+  body: json
+  auth: inherit
+}
+
+body:json {
+  {
+    "title": "Ebook with ISBN-13 (with spaces)",
+    "author": "Test Author",
+    "isbn": "978 0123456789",
+    "description": "Testing ISBN normalization with spaces",
+    "file_path": "/path/to/ebook2.epub",
+    "file_size": 1048576,
+    "mime_type": "application/epub+zip"
+  }
+}
+
+settings {
+  encodeUrl: true
+  timeout: 0
+}
+
+docs {
+  ## Create Ebook with ISBN-13 (with spaces)
+
+  **Expected Behavior:** ISBN should be normalized to `9780123456789`
+
+  This test demonstrates that ISBNs with spaces are automatically normalized.
+}