fix: clear PTZ flag on all MBeg keyboard video inputs

Keyboard interfaces under Clients/GeViIO/GeViIO_01 should never have the
PTZ flag set on their video inputs. Previously PTZ cameras (e.g. 101027)
were exported with PTZ=True on every keyboard, unlike fixed cameras.

Adds geviset.disable_keyboard_ptz() and runs it at the end of the video
input pipeline in both /api/set/export and /api/batch/build. Only the
keyboard interfaces are touched; virtual decoders/servers under
GeViIO_Virtual keep their PTZ flags so PTZ control still works.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/app/geviset.py

@@ -1092,6 +1092,34 @@ def ensure_global_video_inputs(tree, global_ids, ptz_by_id=None):
     )
 
 
+def disable_keyboard_ptz(tree):
+    """Force PTZ off for every video input on every MBeg keyboard interface.
+
+    Keyboards live directly under Clients/GeViIO/GeViIO_01 (each is an
+    interface folder with its own VideoInputs). PTZ control on the keyboard
+    side is never wanted, so the PTZ flag of each video input is cleared.
+    Virtual decoders/servers under GeViIO_Virtual are left untouched.
+    """
+    geviio = _find_folder(tree, ["Clients", "GeViIO", "GeViIO_01"])
+    if not geviio:
+        return 0
+    cleared = 0
+    for interface in geviio.get("children", []):
+        if not isinstance(interface, dict) or interface.get("type") != "folder":
+            continue
+        video_inputs = _child_by_name(interface, "VideoInputs")
+        if video_inputs is None:
+            continue
+        for entry in video_inputs.get("children", []):
+            if entry.get("type") != "folder":
+                continue
+            ptz_node = _child_by_name(entry, "PTZ")
+            if ptz_node is not None and ptz_node.get("value") is not False:
+                ptz_node["value"] = False
+                cleared += 1
+    return cleared
+
+
 def prune_video_inputs(tree, global_ids):
     target_ids = {int(x) for x in global_ids if isinstance(x, int) and x > 0}
     if not target_ids: