feat: align keyboard LocalID to GlobalID and preserve server credentials

Two operator requirements for MBeg keyboards and server connections:

1. align_keyboard_local_ids(): on every keyboard interface under
   Clients/GeViIO/GeViIO_01, set each video input/output LocalID equal to
   its GlobalID so operators can address cameras/monitors by global id.
   Virtual decoders/servers under GeViIO_Virtual keep their sequential
   local ids. Runs after prune in /api/set/export and /api/batch/build.

2. preserve_server_credentials(): server User/Password are entered by hand
   and must survive re-importing the server list from Excel. Matched by
   alias, an existing non-empty credential overrides the imported value.
   Applied to G-Core and GeViScope servers in /api/batch/build.

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

backend/app/geviset.py

@@ -1120,6 +1120,64 @@ def disable_keyboard_ptz(tree):
     return cleared
 
 
+def align_keyboard_local_ids(tree):
+    """Make LocalID equal GlobalID for every video input and output on every
+    MBeg keyboard interface (Clients/GeViIO/GeViIO_01).
+
+    Operators address cameras/monitors on the keyboards by their global id,
+    so the local id must match it. Other interfaces (virtual decoders and
+    servers under GeViIO_Virtual) keep their own sequential local ids.
+    """
+    geviio = _find_folder(tree, ["Clients", "GeViIO", "GeViIO_01"])
+    if not geviio:
+        return 0
+    changed = 0
+    for interface in geviio.get("children", []):
+        if not isinstance(interface, dict) or interface.get("type") != "folder":
+            continue
+        for sub in ("VideoInputs", "VideoOutputs"):
+            container = _child_by_name(interface, sub)
+            if container is None:
+                continue
+            for entry in container.get("children", []):
+                if entry.get("type") != "folder":
+                    continue
+                local_node = _child_by_name(entry, "LocalID")
+                global_node = _child_by_name(entry, "GlobalID")
+                if local_node is None or global_node is None:
+                    continue
+                global_id = global_node.get("value")
+                if isinstance(global_id, int) and local_node.get("value") != global_id:
+                    local_node["value"] = global_id
+                    changed += 1
+    return changed
+
+
+def preserve_server_credentials(new_servers, existing_servers):
+    """Keep User/Password that were already entered on the matching server.
+
+    Server credentials are filled in by hand and must not be wiped when the
+    server list is re-imported from Excel. Servers are matched by alias; an
+    existing non-empty user or password overrides the imported value.
+    """
+    by_alias = {}
+    for server in existing_servers or []:
+        alias = str(server.get("alias", "")).strip()
+        if alias:
+            by_alias[alias] = server
+    preserved = 0
+    for server in new_servers or []:
+        old = by_alias.get(str(server.get("alias", "")).strip())
+        if not old:
+            continue
+        if old.get("user"):
+            server["user"] = old["user"]
+        if old.get("password"):
+            server["password"] = old["password"]
+        preserved += 1
+    return preserved
+
+
 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: