v2: authenticate via app password + use dns.yeil.app public API

Replaces direct dns-server RPC calls (admin shared key, NetBird-only
reachability) with calls to the public /api/v1 surface. The plugin
now logs in with an email + app password, caches the returned Bearer
for the run, then findZone/addRecord/deleteRecord through HTTPS.
Any yeil user with an owned DNS zone can use it from anywhere with
internet access — no more shared key, no NetBird requirement.

INI shape:
  dns_yeil_email = you@yourdomain.com
  dns_yeil_app_password = abcd-efgh-ijkl-mnop
  # dns_yeil_base_url = https://dns.yeil.app  (optional override)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

setup.py

@@ -2,7 +2,7 @@ from setuptools import setup, find_packages
 
 setup(
     name="certbot-dns-yeil",
-    version="1.0.0",
+    version="2.0.0",
     description="yeil DNS Authenticator plugin for Certbot",
     url="https://git.eskimo.dev/Yeil/certbot-dns-yeil",
     author="yeil",