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/config/capabilities.ts

@@ -0,0 +1,49 @@
+export type AppiumCapabilities = Record<string, unknown>;
+
+const COMMON_CAPABILITIES: AppiumCapabilities = {
+  platformName: "Android",
+  "appium:automationName": "UiAutomator2",
+  "appium:deviceName": process.env.DEVICE_NAME || "emulator-5554",
+  "appium:autoGrantPermissions": true,
+  "appium:newCommandTimeout": 300,
+};
+
+/**
+ * Dev Client mode: app is already installed via `expo start --android`.
+ * Appium connects to the running app without reinstalling.
+ */
+const DEV_CLIENT_CAPABILITIES: AppiumCapabilities = {
+  ...COMMON_CAPABILITIES,
+  "appium:appPackage": "host.exp.exponent",
+  "appium:appActivity": ".experience.ExperienceActivity",
+  "appium:noReset": true,
+};
+
+/**
+ * APK mode: Appium installs the APK directly.
+ * Used in CI where the APK is built via `eas build --profile e2e`.
+ */
+function getApkCapabilities(apkPath: string): AppiumCapabilities {
+  return {
+    ...COMMON_CAPABILITIES,
+    "appium:app": apkPath,
+    "appium:noReset": false,
+  };
+}
+
+/**
+ * Returns the appropriate capabilities based on the APK_PATH env variable.
+ * - APK_PATH set → APK mode (CI)
+ * - APK_PATH not set → Dev Client mode (local development)
+ */
+export function getCapabilities(): AppiumCapabilities {
+  const apkPath = process.env.APK_PATH;
+
+  if (apkPath) {
+    console.log(`[Appium] APK mode: ${apkPath}`);
+    return getApkCapabilities(apkPath);
+  }
+
+  console.log("[Appium] Dev Client mode");
+  return DEV_CLIENT_CAPABILITIES;
+}