fix: inline device images as data URIs in offline SVG export

strip_svg_hyperlinks() removed every href, including on <image>
elements that reference device-type photos, leaving devices with
images blank in the exported file. Non-anchor hrefs (currently only
<image>) are now resolved through an optional image_loader callback
and embedded as base64 data URIs instead of being stripped; anchor
unwrapping is unchanged. RackElevationOfflineSVGView wires this up to
NetBox's MEDIA storage.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

netbox_utilities/svg_export.py

@@ -7,20 +7,27 @@ ET.register_namespace("", SVG_NS)
 ET.register_namespace("xlink", XLINK_NS)
 
 _ANCHOR_TAGS = (f"{{{SVG_NS}}}a", "a")
+_IMAGE_TAGS = (f"{{{SVG_NS}}}image", "image")
 _HREF_ATTRS = ("href", f"{{{XLINK_NS}}}href")
 
 
-def strip_svg_hyperlinks(svg_source):
-    """Return svg_source with every <a> wrapper unwrapped and href/xlink:href removed.
+def strip_svg_hyperlinks(svg_source, image_loader=None):
+    """Return svg_source with every <a> wrapper unwrapped and dead links removed.
 
     NetBox wraps rack elevation devices in hyperlinks pointing at internal,
     relative object URLs. Those links are dead weight (and broken paths) once
-    the SVG is saved and opened outside of a NetBox session, so this produces
-    a self-contained file with the same visuals but no link markup.
+    the SVG is saved and opened outside of a NetBox session, so this unwraps
+    them while keeping their contents.
+
+    <image> elements reference device photos by the same kind of internal,
+    relative URL. Simply stripping their href would leave the device blank,
+    so image_loader (href -> "data:...;base64,..." or None) is used to embed
+    the image data directly instead. Without an image_loader, image hrefs are
+    left untouched.
     """
     root = ET.fromstring(svg_source)
     _unwrap_anchors(root)
-    _strip_href_attributes(root)
+    _resolve_hrefs(root, image_loader)
     return ET.tostring(root, encoding="unicode")
 
 
@@ -41,8 +48,20 @@ def _unwrap_anchors(parent):
             parent.append(child)
 
 
-def _strip_href_attributes(element):
-    for attr in _HREF_ATTRS:
-        element.attrib.pop(attr, None)
+def _resolve_hrefs(element, image_loader):
+    if element.tag in _IMAGE_TAGS:
+        if image_loader is not None:
+            for attr in _HREF_ATTRS:
+                href = element.attrib.get(attr)
+                if not href:
+                    continue
+                data_uri = image_loader(href)
+                if data_uri:
+                    element.attrib[attr] = data_uri
+                else:
+                    element.attrib.pop(attr, None)
+    else:
+        for attr in _HREF_ATTRS:
+            element.attrib.pop(attr, None)
     for child in element:
-        _strip_href_attributes(child)
+        _resolve_hrefs(child, image_loader)