bos-settings 0.4.1: fix broken panels, add breadsearch view

- breadbox panel edited [[contexts]] but breadbox reads [[context]]
  (serde rename mismatch) — panel was always empty and Save appended
  a dead array.
- Packages panel parsed installed.json as a flat map instead of
  unwrapping {"packages": {...}} — always showed one bogus row.
- load_doc silently produced an empty document on any parse error,
  so the next Save could clobber a config file with a syntax typo;
  now backs it up first.
- Hyprland panel opened hyprland.conf/keybinds.conf (BOS ships
  hyprland.lua) via $EDITOR with no terminal (dead click for any TUI
  editor) and defaulted to foot (BOS ships kitty). Now opens
  hyprland.lua and a keybinds cheat sheet via kitty -e $EDITOR.
- New breadsearch view: power (enabled/run-on-battery), compute
  backend (cpu/npu/rocm), index/search settings.

bos-settings/src/ui/sidebar.rs

@@ -12,6 +12,7 @@ pub const APPS_ITEMS: &[SidebarItem] = &[
     SidebarItem { id: "breadbox",    label: "breadbox"    },
     SidebarItem { id: "breadcrumbs", label: "breadcrumbs" },
     SidebarItem { id: "breadpad",    label: "breadpad"    },
+    SidebarItem { id: "breadsearch", label: "breadsearch" },
 ];
 
 pub const SYSTEM_ITEMS: &[SidebarItem] = &[