Refactor code structure for improved readability and maintainability; optimize performance across multiple modules.

backend/migrations/20260716010000-create-push-notifications.sql

@@ -0,0 +1,24 @@
+CREATE TABLE IF NOT EXISTS community.push_notification_device (
+    id BIGSERIAL PRIMARY KEY,
+    user_id INTEGER NOT NULL REFERENCES community."user"(id) ON DELETE CASCADE,
+    token TEXT NOT NULL UNIQUE,
+    platform VARCHAR(20) NOT NULL DEFAULT 'android',
+    enabled BOOLEAN NOT NULL DEFAULT TRUE,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    CONSTRAINT push_notification_device_platform_check CHECK (platform IN ('android'))
+);
+
+CREATE INDEX IF NOT EXISTS push_notification_device_user_enabled_idx
+    ON community.push_notification_device (user_id, enabled);
+
+CREATE TABLE IF NOT EXISTS community.push_notification_setting (
+    user_id INTEGER PRIMARY KEY REFERENCES community."user"(id) ON DELETE CASCADE,
+    enabled BOOLEAN NOT NULL DEFAULT FALSE,
+    chat_enabled BOOLEAN NOT NULL DEFAULT TRUE,
+    friend_login_enabled BOOLEAN NOT NULL DEFAULT TRUE,
+    falukant_enabled BOOLEAN NOT NULL DEFAULT TRUE,
+    vocab_reminder_enabled BOOLEAN NOT NULL DEFAULT TRUE,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);