Add E2E testing infrastructure with WebdriverIO + Appium

Set up E2E test framework for Android using WebdriverIO, Appium, and
UiAutomator2. Add testID props to key components (AuthButton, BaseButton,
ChatBubble, CustomTextInput, ProposedEventCard) and apply testIDs to
login screen, chat screen, tab bar, and settings. Include initial tests
for app launch detection and login flow validation. Update CLAUDE.md
with E2E docs.

apps/client/e2e/helpers/driver.ts

@@ -0,0 +1,41 @@
+import { remote, type Browser } from "webdriverio";
+import { getCapabilities } from "../config/capabilities";
+
+let driver: Browser | null = null;
+
+const APPIUM_HOST = process.env.APPIUM_HOST || "localhost";
+const APPIUM_PORT = parseInt(process.env.APPIUM_PORT || "4723", 10);
+
+/**
+ * Initialize the Appium driver. If already initialized, returns the existing instance.
+ * With --runInBand, all test files share this singleton.
+ */
+export async function initDriver(): Promise<Browser> {
+  if (driver) return driver;
+
+  const capabilities = getCapabilities();
+
+  driver = await remote({
+    hostname: APPIUM_HOST,
+    port: APPIUM_PORT,
+    path: "/",
+    capabilities,
+    logLevel: "warn",
+  });
+
+  return driver;
+}
+
+export function getDriver(): Browser {
+  if (!driver) {
+    throw new Error("Driver not initialized. Call initDriver() first.");
+  }
+  return driver;
+}
+
+export async function quitDriver(): Promise<void> {
+  if (driver) {
+    await driver.deleteSession();
+    driver = null;
+  }
+}