fix: allow hyphens, dots, and underscores in Dialpad meeting URL validation (#28253)

The Dialpad conferencing integration's URL regex only accepted
alphanumeric characters in the meeting room path ([a-zA-Z0-9]+),
causing valid personal meeting URLs containing hyphens, dots, or
underscores to fail validation.

For example, https://meetings.dialpad.com/mmit-russ is rejected
despite being a valid Dialpad personal meeting link. The sample URL
shown in the error message (alphanumeric only) passes, but
real-world room names commonly use hyphens and other characters.

Updated the urlRegExp character class from [a-zA-Z0-9] to
[a-zA-Z0-9._-] to match all valid Dialpad meeting room slugs.

Fixes issue introduced in #15444.

Co-authored-by: Sahitya Chandra <sahityajb@gmail.com>

packages/app-store/dialpad/config.json

@@ -15,7 +15,7 @@
       "label": "{TITLE}",
       "linkType": "static",
       "organizerInputPlaceholder": "https://meetings.dialpad.com/adb2002",
-      "urlRegExp": "^https:\\/\\/meetings\\.dialpad\\.com\\/[a-zA-Z0-9]+$"
+      "urlRegExp": "^https:\\/\\/meetings\\.dialpad\\.com\\/[a-zA-Z0-9._-]+$"
     }
   },
   "description": "A new way to meet, with built-in Ai",