dsh-dsbal: DeepSeek Balance Widget for the DSH Sidebar

The DSH Web sidebar plugin `dsh-dsbal` is used to display the CNY balance of a DeepSeek API. It adds a balance button above the Settings button at the bottom of the sidebar, automatically refreshing every 30 seconds by default while also supporting manual refresh. Hovering over the button displays the total balance, peak/off-peak pricing, and detailed breakdown. It also supports changing the border color based on balance thresholds (<50/30/10)—yellow, orange, or red—as an alert. The plugin is view-only, and the refresh interval is fixed. To install it, run the specified command in a terminal, then restart `dsh web` and hard-refresh the browser after installation.