feat: enable HTTPS admin panel on port 443 for new deployments

Add Nginx SSL panel config, enable-panel-https.sh, secure Flask cookies, and update docs for https login.

Co-authored-by: Cursor <cursoragent@cursor.com>

panel/app.py

@@ -52,7 +52,8 @@ _panel_path = os.environ.get("PANEL_PATH", "").strip().strip("/")
 _panel_domain = os.environ.get("PANEL_DOMAIN", "").strip()
 if _panel_path:
     app.config["SESSION_COOKIE_PATH"] = f"/{_panel_path}/"
-    app.config["PREFERRED_URL_SCHEME"] = "http"
+    app.config["PREFERRED_URL_SCHEME"] = "https"
+    app.config["SESSION_COOKIE_SECURE"] = True
     app.wsgi_app = ProxyFix(
         app.wsgi_app, x_for=1, x_proto=1, x_host=0, x_prefix=0
     )
@@ -71,7 +72,7 @@ class _PanelPrefixMiddleware:
         if self.domain and not environ.get("HTTP_HOST"):
             environ["HTTP_HOST"] = self.domain
         if not environ.get("HTTP_X_FORWARDED_PROTO"):
-            environ["HTTP_X_FORWARDED_PROTO"] = "http"
+            environ["HTTP_X_FORWARDED_PROTO"] = "https"
         return self.app(environ, start_response)