feat: Add role-based access control to database schema

- Add role column to users table with admin/user constraint
- Add added_by_admin_id column to ebooks table for tracking
- Add constraint to ensure only admins can manage folders
- Update all SQL queries to include role field
- Regenerate database models with new schema

database/schema/schema.sql

@@ -9,6 +9,7 @@ CREATE TABLE users (
     password_hash VARCHAR(255) NOT NULL,
     first_name VARCHAR(255),
     last_name VARCHAR(255),
+    role VARCHAR(20) NOT NULL DEFAULT 'user' CHECK (role IN ('admin', 'user')),
     theme VARCHAR(50) DEFAULT 'tokyo-night',
     scan_frequency_minutes INTEGER DEFAULT 60,
     auto_scan_enabled BOOLEAN DEFAULT true,
@@ -34,6 +35,7 @@ CREATE TABLE ebooks (
     date_published DATE,
     publisher VARCHAR(255),
     contributors TEXT,
+    added_by_admin_id UUID REFERENCES users(id) ON DELETE SET NULL,
     created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
     updated_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
 );
@@ -66,7 +68,10 @@ CREATE TABLE user_ebook_folders (
     user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
     folder_path VARCHAR(500) NOT NULL,
     created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
-    UNIQUE(user_id, folder_path)
+    UNIQUE(user_id, folder_path),
+    CONSTRAINT admin_only_folder CHECK (EXISTS (
+        SELECT 1 FROM users WHERE id = user_id AND role = 'admin'
+    ))
 );
 
 -- Create indexes for better query performance
@@ -74,6 +79,7 @@ CREATE INDEX idx_users_email ON users(email);
 CREATE INDEX idx_users_username ON users(username);
 CREATE INDEX idx_ebooks_title ON ebooks(title);
 CREATE INDEX idx_ebooks_author ON ebooks(author);
+CREATE INDEX idx_ebooks_added_by_admin_id ON ebooks(added_by_admin_id);
 CREATE INDEX idx_reading_progress_ebook_id ON reading_progress(ebook_id);
 CREATE INDEX idx_reading_progress_user_id ON reading_progress(user_id);
 CREATE INDEX idx_ebook_ratings_ebook_id ON ebook_ratings(ebook_id);
@@ -81,4 +87,11 @@ CREATE INDEX idx_ebook_ratings_user_id ON ebook_ratings(user_id);
 CREATE INDEX idx_user_ebook_folders_user_id ON user_ebook_folders(user_id);
 
 -- Add comment explaining the rating system
-COMMENT ON COLUMN ebook_ratings.rating IS 'Rating scale 1-10 (odd numbers = half-stars: 1,3,5,7,9 = 0.5,1.5,2.5,3.5,4.5 stars)';
+COMMENT ON COLUMN ebook_ratings.rating IS 'Rating scale 1-10 (odd numbers = half-stars: 1,3,5,7,9 = 0.5,1.5,2.5,3.5,4.5 stars)';
+
+-- Role System Notes:
+-- - All users default to 'user' role
+-- - Admin users can: add/edit/delete folders, scan ebooks, modify ebook metadata, delete ebooks
+-- - Regular users can: view all ebooks, rate ebooks, track reading progress, manage their profile
+-- - To create first admin: UPDATE users SET role = 'admin' WHERE email = 'your-admin-email';
+-- - Only admins can manage folders and ebook metadata