FIX: Database initialization and .env example

Remove createion of table and relationship because of sequelize in nodejs server create this relation

+# Database Configuration
 TZ=Asia/Seoul
 MYSQL_HOST={YOUR_MYSQL_HOST}
 MYSQL_PORT={YOUR_MYSQL_PORT}

 CREATE DATABASE mamuri_db;
-
-USE mamuri_db;
-
-CREATE TABLE user
-(
-    id      INT AUTO_INCREMENT PRIMARY KEY,
-    user_id INT NOT NULL
-);
-
-CREATE TABLE keyword
-(
-    id      INT AUTO_INCREMENT PRIMARY KEY,
-    keyword VARCHAR(150) NULL
-);
-
-CREATE TABLE user_keyword
-(
-    id         INT AUTO_INCREMENT PRIMARY KEY,
-    user_id    INT NOT NULL,
-    keyword_id INT NOT NULL,
-    FOREIGN KEY (user_id) REFERENCES user (id) ON DELETE CASCADE,
-    FOREIGN KEY (keyword_id) REFERENCES keyword (id) ON DELETE CASCADE
-);
-
-CREATE TABLE item
-(
-    id            INT AUTO_INCREMENT PRIMARY KEY,
-    keyword_id    INT          NOT NULL,
-    platform      VARCHAR(50)  NOT NULL,
-    name          VARCHAR(100) NOT NULL,
-    price         INT          NOT NULL,
-    thumbnail_url VARCHAR(255) NULL,
-    item_url      VARCHAR(255) NOT NULL,
-    extra_info    TEXT         NULL,
-    created_at    DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP
-);
-
-CREATE TABLE item_check
-(
-    id      INT AUTO_INCREMENT PRIMARY KEY,
-    item_id INT NULL,
-    user_id INT NULL,
-    FOREIGN KEY (item_id) REFERENCES item (id) ON DELETE CASCADE,
-    FOREIGN KEY (user_id) REFERENCES user (id) ON DELETE CASCADE
-);
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