refactor: restructure project from bookmann to shelf

- Rename project from 'bookmann' to 'shelf'
- Move all backend/ contents to root level (flatten structure)
- Update Go module name from 'bookmann' to 'shelf'
- Update all import paths to use new 'shelf' module
- Update Dockerfile to work without backend/ subdirectory
- Update docker-compose.yml to use new structure and rename containers
- Update .gitignore for new file paths
- Update README.md with new project name and structure
- Regenerate database code with new module imports

migrations/001_create_tables.up.sql

@@ -0,0 +1,44 @@
+-- Create users table
+CREATE TABLE users (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    email VARCHAR(255) UNIQUE NOT NULL,
+    username VARCHAR(255) UNIQUE NOT NULL,
+    password_hash VARCHAR(255) NOT NULL,
+    theme VARCHAR(50) DEFAULT 'tokyo-night',
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    updated_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
+);
+
+-- Create ebooks table
+CREATE TABLE ebooks (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    title VARCHAR(255) NOT NULL,
+    author VARCHAR(255),
+    isbn VARCHAR(13),
+    description TEXT,
+    file_path VARCHAR(500) NOT NULL,
+    file_size BIGINT,
+    mime_type VARCHAR(100),
+    cover_image_path VARCHAR(500),
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    updated_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
+);
+
+-- Create reading_progress table
+CREATE TABLE reading_progress (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    ebook_id UUID NOT NULL REFERENCES ebooks(id) ON DELETE CASCADE,
+    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    current_page INTEGER DEFAULT 0,
+    total_pages INTEGER,
+    last_read_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    UNIQUE(ebook_id, user_id)
+);
+
+-- Create indexes
+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_reading_progress_ebook_id ON reading_progress(ebook_id);
+CREATE INDEX idx_reading_progress_user_id ON reading_progress(user_id);