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/External/SquireUI.js

@@ -38,13 +38,13 @@ class SquireUI
 		const
 			clr = createElement('input'),
 			doClr = name => input => {
-				// https://github.com/nextgen-networks/snappymail/issues/826
+				// https://github.com/the-djmaze/snappymail/issues/826
 				clr.style.left = (input.offsetLeft + input.parentNode.offsetLeft) + 'px';
 				clr.style.width = input.offsetWidth + 'px';
 
 				clr.value = '';
 				clr.onchange = () => squire.setStyle({[name]:clr.value});
-				// Chrome 110+ https://github.com/nextgen-networks/snappymail/issues/1199
+				// Chrome 110+ https://github.com/the-djmaze/snappymail/issues/1199
 //				clr.oninput = () => squire.setStyle({[name]:clr.value});
 				setTimeout(()=>clr.click(),1);
 			},
@@ -263,7 +263,7 @@ class SquireUI
 
 		clr.type = 'color';
 		toolbar.append(clr);
-		// Chrome https://github.com/nextgen-networks/snappymail/issues/1199
+		// Chrome https://github.com/the-djmaze/snappymail/issues/1199
 		let clrid = 'squire-colors',
 			colorlist = doc.getElementById(clrid),
 			add = hex => colorlist.append(new Option(hex));