Add character rename to admin panel

Renaming checks for a name collision first (characters.char_name has
no unique constraint in the schema, so this has to be enforced at the
application level to avoid two characters silently sharing a name),
and also updates list_friend.namefriend for any rows referencing this
character's id -- that column is a denormalized display-name cache in
other players' friend lists and would otherwise go stale on rename.

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

webadmin/app.py

@@ -258,6 +258,37 @@ def edit_character(char_id):
     db = get_db()
     try:
         if request.method == "POST":
+            with db.cursor() as cur:
+                cur.execute("SELECT char_name FROM characters WHERE id=%s", (char_id,))
+                old = cur.fetchone()
+            if not old:
+                flash("Charakter nicht gefunden.")
+                return redirect(url_for("characters"))
+
+            new_name = request.form.get("char_name", "").strip()
+            if new_name and new_name != old["char_name"]:
+                with db.cursor() as cur:
+                    cur.execute(
+                        "SELECT id FROM characters WHERE char_name=%s AND id<>%s",
+                        (new_name, char_id),
+                    )
+                    if cur.fetchone():
+                        flash(f"Name '{new_name}' ist bereits vergeben.")
+                        return redirect(url_for("edit_character", char_id=char_id))
+                    cur.execute(
+                        "UPDATE characters SET char_name=%s WHERE id=%s",
+                        (new_name, char_id),
+                    )
+                    # namefriend is a denormalized display-name cache in other
+                    # players' friend lists (list_friend.idfriend references
+                    # this character's id) -- keep it in sync so renames
+                    # don't leave stale names in friend lists.
+                    cur.execute(
+                        "UPDATE list_friend SET namefriend=%s WHERE idfriend=%s",
+                        (new_name, char_id),
+                    )
+                flash(f"Charakter '{old['char_name']}' umbenannt in '{new_name}'.")
+
             values = []
             set_clauses = []
             for field in CHAR_STAT_FIELDS: