feat: Introduce knex for database migrations

- Adds knex.js to manage database schema changes systematically.
- Creates an initial migration file based on `hyungi_schema_v2.sql` to represent the current database state.
- Adds npm scripts (`db:migrate`, `db:rollback`, etc.) for easy execution of migration tasks.
- Archives legacy SQL files and old migration scripts into the `db_archive/` directory to prevent confusion and clean up the project structure.

api.hyungi.net/db/migrations/20251219003210_20251219_initial_schema.js

@@ -0,0 +1,49 @@
+const fs = require('fs');
+const path = require('path');
+
+/**
+ * @param { import("knex").Knex } knex
+ * @returns { Promise<void> }
+ */
+exports.up = function(knex) {
+  const schemaSql = fs.readFileSync(path.join(__dirname, '../../hyungi_schema_v2.sql'), 'utf8');
+  return knex.raw(schemaSql);
+};
+
+/**
+ * @param { import("knex").Knex } knex
+ * @returns { Promise<void> }
+ */
+exports.down = function(knex) {
+  // down 마이그레이션은 모든 테이블을 역순으로 삭제하도록 구현합니다.
+  const tables = [
+    'cutting_plans',
+    'daily_issue_reports',
+    'daily_work_reports',
+    'codes',
+    'code_types',
+    'factory_info',
+    'equipment_list',
+    'pipe_specs',
+    'tasks',
+    'worker_groups',
+    'workers',
+    'projects',
+    'password_change_logs',
+    'login_logs',
+    'users'
+  ];
+  
+  // 외래 키 제약 조건을 먼저 비활성화합니다.
+  return knex.raw('SET FOREIGN_KEY_CHECKS = 0;')
+    .then(() => {
+      // 각 테이블을 순회하며 drop table if exists를 실행합니다.
+      return tables.reduce((promise, tableName) => {
+        return promise.then(() => knex.schema.dropTableIfExists(tableName));
+      }, Promise.resolve());
+    })
+    .finally(() => {
+      // 외래 키 제약 조건을 다시 활성화합니다.
+      return knex.raw('SET FOREIGN_KEY_CHECKS = 1;');
+    });
+};