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

internal/database/queries/queries.sql

@@ -0,0 +1,111 @@
+-- name: CreateUser :one
+INSERT INTO users (email, username, password_hash, theme)
+VALUES ($1, $2, $3, $4)
+RETURNING *;
+
+-- name: GetUserByEmail :one
+SELECT * FROM users WHERE email = $1;
+
+-- name: GetUserByUsername :one
+SELECT * FROM users WHERE username = $1;
+
+-- name: GetUserByEmailOrUsername :one
+SELECT * FROM users WHERE email = $1 OR username = $1;
+
+-- name: GetUser :one
+SELECT id, email, username, theme, created_at, updated_at FROM users WHERE id = $1;
+
+-- name: ListUsers :many
+SELECT id, email, username, theme, created_at, updated_at FROM users ORDER BY created_at DESC;
+
+-- name: GetEbook :one
+SELECT * FROM ebooks WHERE id = $1;
+
+-- name: ListEbooks :many
+SELECT * FROM ebooks ORDER BY created_at DESC LIMIT $1 OFFSET $2;
+
+-- name: CreateEbook :one
+INSERT INTO ebooks (title, author, isbn, description, file_path, file_size, mime_type, cover_image_path, series, series_number, tags, asin, date_published, publisher, contributors)
+VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15)
+RETURNING *;
+
+-- name: UpdateEbook :one
+UPDATE ebooks SET
+    title = $2,
+    author = $3,
+    isbn = $4,
+    description = $5,
+    cover_image_path = $6,
+    series = $7,
+    series_number = $8,
+    tags = $9,
+    asin = $10,
+    date_published = $11,
+    publisher = $12,
+    contributors = $13,
+    updated_at = NOW()
+WHERE id = $1
+RETURNING *;
+
+-- name: DeleteEbook :exec
+DELETE FROM ebooks WHERE id = $1;
+
+-- name: GetReadingProgress :one
+SELECT * FROM reading_progress WHERE ebook_id = $1 AND user_id = $2;
+
+-- name: UpdateReadingProgress :one
+INSERT INTO reading_progress (ebook_id, user_id, current_page, total_pages, last_read_at)
+VALUES ($1, $2, $3, $4, NOW())
+ON CONFLICT (ebook_id, user_id)
+DO UPDATE SET
+    current_page = EXCLUDED.current_page,
+    total_pages = EXCLUDED.total_pages,
+    last_read_at = NOW()
+RETURNING *;
+
+-- name: DeleteReadingProgress :exec
+DELETE FROM reading_progress WHERE ebook_id = $1 AND user_id = $2;
+
+-- name: UpdateUserTheme :exec
+UPDATE users SET theme = $2, updated_at = NOW() WHERE id = $1;
+
+-- name: CreateEbookRating :one
+INSERT INTO ebook_ratings (ebook_id, user_id, rating)
+VALUES ($1, $2, $3)
+ON CONFLICT (ebook_id, user_id)
+DO UPDATE SET
+    rating = EXCLUDED.rating,
+    updated_at = NOW()
+RETURNING *;
+
+-- name: GetEbookRating :one
+SELECT * FROM ebook_ratings WHERE ebook_id = $1 AND user_id = $2;
+
+-- name: GetEbookRatings :many
+SELECT er.*, u.username
+FROM ebook_ratings er
+JOIN users u ON er.user_id = u.id
+WHERE er.ebook_id = $1
+ORDER BY er.created_at DESC;
+
+-- name: UpdateEbookRating :one
+UPDATE ebook_ratings SET
+    rating = $3,
+    updated_at = NOW()
+WHERE ebook_id = $1 AND user_id = $2
+RETURNING *;
+
+-- name: DeleteEbookRating :exec
+DELETE FROM ebook_ratings WHERE ebook_id = $1 AND user_id = $2;
+
+-- name: AddUserEbookFolder :one
+INSERT INTO user_ebook_folders (user_id, folder_path) VALUES ($1, $2) RETURNING *;
+
+-- name: GetUserEbookFolders :many
+SELECT * FROM user_ebook_folders WHERE user_id = $1 ORDER BY created_at;
+
+-- name: DeleteUserEbookFolder :exec
+DELETE FROM user_ebook_folders WHERE user_id = $1 AND folder_path = $2;
+
+-- name: GetEbookByFilePath :one
+SELECT * FROM ebooks WHERE file_path = $1;