feat: add qr code alternative sign in method

backend/resources/migrations/sqlite/20260713120000_device_login_requests.down.sql

@@ -0,0 +1 @@
+DROP TABLE device_login_requests;

backend/resources/migrations/sqlite/20260713120000_device_login_requests.up.sql

@@ -0,0 +1,20 @@
+PRAGMA foreign_keys=OFF;
+BEGIN;
+
+CREATE TABLE device_login_requests
+(
+    id                TEXT     NOT NULL PRIMARY KEY,
+    created_at        DATETIME NOT NULL,
+    code              TEXT     NOT NULL UNIQUE,
+    device_token_hash TEXT     NOT NULL UNIQUE,
+    status            TEXT     NOT NULL CHECK (status IN ('pending', 'approved', 'denied')),
+    expires_at        DATETIME NOT NULL,
+    ip_address        TEXT     NOT NULL,
+    user_agent        TEXT     NOT NULL,
+    user_id           TEXT REFERENCES users ON DELETE CASCADE
+);
+
+CREATE INDEX idx_device_login_requests_expires_at ON device_login_requests (expires_at);
+
+COMMIT;
+PRAGMA foreign_keys=ON;