Move ai-stack and paintplus vendored source under vendor/

Matches the existing vendor/easy-asterisk convention (used by
services/asterisk.sh) instead of two one-off top-level directories that
cluttered the repo root and didn't look like anything else next to
setup.sh, lib/, services/, extras/. Only the two services' own SRC_DIR
path resolution and header comments needed updating — nothing else in
the repo referenced the old ./ai-stack / ./paintplus paths.

Also documents vendor/ in README.md's Layout section.

vendor/paintplus/frontend/src/css/print.css

@@ -0,0 +1,34 @@
+@media print{
+	body{
+		background:none !important;
+		background: #fff;
+		background-color: #fff;
+		font-family: Arial,Helvetica,Verdana;
+		width:auto !important;
+		padding:5px !important;
+		font-size: 12px;
+	}
+	progress,
+	.menu,
+	.sidebar_left,
+	.sidebar_right,
+	.submenu,
+	.main_menu{
+		display: none;
+		height: 0;
+		width: 0;
+	}
+	.main_wrapper{
+		margin:0px;
+		padding:0px;
+	}
+	canvas{
+		border:0px;
+		position: absolute;
+		top:0px;
+		left:0px;
+	}
+	.canvas_wrapper canvas{
+		border:0;
+	}
+}