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

database/schema/schema.sql

@@ -73,13 +73,25 @@ CREATE TABLE library_visibility (
     UNIQUE(user_id, library_id)
 );
 
+-- ISBN normalization function
+-- Removes hyphens and spaces from ISBN to standardize format
+CREATE OR REPLACE FUNCTION normalize_isbn(isbn TEXT) RETURNS TEXT AS $$
+BEGIN
+    IF isbn IS NULL THEN
+        RETURN NULL;
+    END IF;
+    -- Remove hyphens and spaces, return only digits and X (for ISBN-10)
+    RETURN regexp_replace(isbn, '[-\s]', '', 'g');
+END;
+$$ LANGUAGE plpgsql IMMUTABLE;
+
 -- Create media_items table (replaces ebooks table for broader media support)
 CREATE TABLE media_items (
     id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
     library_id UUID NOT NULL REFERENCES libraries(id) ON DELETE CASCADE,
     title VARCHAR(255) NOT NULL,
     author VARCHAR(255),
-    isbn VARCHAR(13), -- Still relevant for ebooks
+    isbn VARCHAR(17), -- Supports ISBN-13 with hyphens (up to 17 chars)
     description TEXT,
     file_path VARCHAR(500) NOT NULL,
     file_size BIGINT,
@@ -195,6 +207,22 @@ WHERE lt.name = 'ebooks';
 -- Note: user_ebook_folders table is replaced by library_folders table
 -- Libraries now handle folder management instead of individual users
 
+-- ISBN normalization trigger
+-- Automatically normalizes ISBN on insert and update
+CREATE OR REPLACE FUNCTION normalize_media_item_isbn() RETURNS TRIGGER AS $$
+BEGIN
+    IF NEW.isbn IS NOT NULL THEN
+        NEW.isbn := normalize_isbn(NEW.isbn);
+    END IF;
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE TRIGGER trigger_normalize_media_item_isbn
+    BEFORE INSERT OR UPDATE ON media_items
+    FOR EACH ROW
+    EXECUTE FUNCTION normalize_media_item_isbn();
+
 -- Create indexes for better query performance
 CREATE INDEX idx_users_email ON users(email);
 CREATE INDEX idx_users_username ON users(username);