feat(e2e): add Playwright end-to-end tests for authentication, GRN, production, stock transfers, and adjustments

- Introduced Playwright configuration for e2e testing.
- Implemented authentication tests to validate login functionality.
- Created tests for GRN (Goods Receipt Note) to ensure proper stock handling.
- Developed production run tests to verify lifecycle and stock posting.
- Added stock transfer tests to check movement between warehouses.
- Implemented stock adjustment tests for positive and negative adjustments.
- Established API seeder for test data setup and verification.
- Enhanced utility functions for UI interactions and response handling.

Testing/e2e/playwright.config.ts

@@ -0,0 +1,35 @@
+import { defineConfig, devices } from "@playwright/test"
+import { env, AUTH_STORAGE_STATE } from "./support/env"
+
+export default defineConfig({
+  testDir: "./specs",
+  fullyParallel: false, // specs share warehouse/item reference data via the ledger - keep runs serial per file
+  forbidOnly: !!process.env.CI,
+  retries: process.env.CI ? 1 : 0,
+  // Multiple workers hit the local dev backend concurrently across spec files and it can't
+  // take it: confirmed reference-data GETs (e.g. /warehouses) intermittently 500 under 2+
+  // workers against a plain `dotnet run` + local Postgres, and pass every time at workers: 1.
+  // Bump this only against a backend that can actually take concurrent load (a real CI service
+  // container, not a single dev-mode process).
+  workers: 1,
+  reporter: [["html", { open: "never" }], ["list"]],
+  timeout: 45_000,
+  expect: { timeout: 10_000 },
+  use: {
+    baseURL: env.baseUrl,
+    trace: "on-first-retry",
+    screenshot: "only-on-failure",
+    video: "retain-on-failure",
+  },
+  projects: [
+    {
+      name: "setup",
+      testMatch: /global\.setup\.ts/,
+    },
+    {
+      name: "chromium",
+      use: { ...devices["Desktop Chrome"], storageState: AUTH_STORAGE_STATE },
+      dependencies: ["setup"],
+    },
+  ],
+})