chore: archive QuickNav and ZTools into reference folder (#345)

Copy QuickNav and ZTools source trees into reference/ for developer
reference during the UI/UX rework. These are plain directories (not
submodules) and are not included in the build.

- reference/quicknav/ — QuickNav addon source
- reference/ztools/ — ZTools addon source

Part of the UI/UX rework preparation. See #346.

reference/quicknav/package.xml

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<package format="1" xmlns="https://wiki.freecad.org/Package_Metadata">
+  <name>QuickNav</name>
+  <description>Keyboard-driven command navigation</description>
+  <version>0.1.0</version>
+  <maintainer email="dev@kindred-systems.com">Kindred Systems</maintainer>
+  <license>LGPL-2.1</license>
+  <url type="repository">https://git.kindred-systems.com/kindred/quicknav</url>
+
+  <content>
+    <workbench>
+      <classname>QuickNavWorkbench</classname>
+      <subdirectory>./</subdirectory>
+    </workbench>
+  </content>
+
+  <kindred>
+    <min_create_version>0.1.0</min_create_version>
+    <load_priority>20</load_priority>
+    <pure_python>true</pure_python>
+    <dependencies>
+      <dependency>sdk</dependency>
+    </dependencies>
+  </kindred>
+</package>