Update repository URLs to nextgen-networks while preserving deep links

Replaced bare references to the-djmaze/snappymail with nextgen-networks/snappymail/
and updated .git URLs to the new organization.

Per user request:
- README files are excluded.
- URLs with a trailing slash (e.g. issues, pull requests, releases) are
  left pointing to the original repository to preserve historical context.
- Bare web URLs now include the requested trailing slash.
- Existing nextgen-networks bare URLs were updated to include the trailing slash.

Co-authored-by: nextgen-networks <21206978+nextgen-networks@users.noreply.github.com>

dev/Component/EmailAddresses.js

@@ -143,7 +143,7 @@ export class EmailAddressesComponent {
 								datalist.append(new Option(item));
 								chars = Math.max(chars, item.length);
 							});
-							// https://github.com/nextgen-networks/snappymail/issues/368 and #513
+							// https://github.com/the-djmaze/snappymail/issues/368 and #513
 							chars *= 8;
 							if (input.clientWidth < chars) {
 								input.style.width = chars + 'px';