Remove standalone fetcher, add setup tool with install/uninstall workflow

Drop claude-fetcher binary and cron job — the widget's built-in
BackgroundFetcher is the sole fetcher now. Add cmd/setup with cross-platform
install and uninstall (--uninstall): kills widget, removes binaries + autostart,
cleans Claude Code statusline setting, optionally removes config dir.

Also includes: browser-based login (chromedp), ICO wrapper for Windows tray
icon, and reduced icon size (64px).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packaging/linux/claude-statusline-fetch

@@ -1,3 +0,0 @@
-# Fetch Claude API usage every 5 minutes (all users with a session key)
-# Installed by claude-statusline package
-*/5 * * * * root /usr/bin/claude-fetcher 2>/dev/null

packaging/nfpm.yaml

@@ -6,7 +6,7 @@ section: utils
 priority: optional
 maintainer: Axel Meyer <axel.meyer@durania.net>
 description: |
-  Claude API usage monitor — CLI statusline, cron fetcher, and desktop tray widget.
+  Claude API usage monitor — CLI statusline and desktop tray widget.
   Shows 5-hour and 7-day token usage from claude.ai in your terminal or system tray.
 vendor: davoryn.de
 homepage: https://git.davoryn.de/calic/claude-statusline
@@ -18,11 +18,6 @@ contents:
     file_info:
       mode: 0755
 
-  - src: ./claude-fetcher
-    dst: /usr/bin/claude-fetcher
-    file_info:
-      mode: 0755
-
   - src: ./claude-widget
     dst: /usr/bin/claude-widget
     file_info:
@@ -33,11 +28,6 @@ contents:
     file_info:
       mode: 0644
 
-  - src: ./packaging/linux/claude-statusline-fetch
-    dst: /etc/cron.d/claude-statusline-fetch
-    file_info:
-      mode: 0644
-
 scripts:
   postinstall: ./packaging/linux/postinstall.sh
   preremove: ./packaging/linux/preremove.sh