feat: add Android browser preset for companion device registration (#248)

* feat: add Android browser preset for companion device registration

Add Browsers.android(apiLevel) preset that identifies as an Android
companion device (SMB_ANDROID platform, ANDROID_PHONE device type).
Validated against Frida captures of real WhatsApp Android protocol.


* feat: support BAILEYS_BROWSER env var for browser selection

Allows selecting Android companion mode via environment variable
without code changes. Set BAILEYS_BROWSER=android (or android:15
for a specific API level) to register as an Android device.

* fix: auto-detect Android browser in pair code and fall back to Chrome

Pair code companion registration fails with Android browser because the
WA server rejects the ANDROID_PHONE companion_platform_id over the web
Noise protocol. When Android is detected, requestPairingCode() now
transparently uses Chrome/macOS platform values for the pair code stanza
while QR code pairing continues to work as Android (SMB_ANDROID).

* docs: add android to isValidBrowserPreset JSDoc

src/Types/index.ts

@@ -23,6 +23,7 @@ export type BrowsersMap = {
 	baileys(browser: string): [string, string, string]
 	windows(browser: string): [string, string, string]
 	appropriate(browser: string): [string, string, string]
+	android(apiLevel: string): [string, string, string]
 }
 
 export enum DisconnectReason {