Submit Formatting Button State

Goal

Make the code submission button reflect the automatic formatting request that runs before submission.

For Python3, C, and C++, the button displays 格式化中 while the formatting API request is pending.
During formatting, the button uses the existing loading icon and is disabled to prevent duplicate submissions.
After formatting succeeds, the existing submission flow continues and the button can display 正在提交.
A formatting error stops submission and clears the formatting state before showing the existing warning.
A formatter server or network failure keeps the existing fallback behavior: clear the formatting state and submit the original code.
Languages without automatic formatting skip this state and submit directly.
Existing button labels and judging/cooldown behavior remain unchanged.

Add a component-local isFormatting ref in SubmitCode.vue.

Include it in submitDisabled.
Give it priority in submitLabel, using 格式化中.
Include it in the loading-icon condition.
Set it immediately before formatCode.
Clear it in a finally block so every formatter outcome restores the button state.

The state remains local because it is transient UI state owned only by the submission button.

The frontend currently has no automated test suite. Verify with:

TypeScript production build.
Manual inspection of the state transitions for successful formatting, formatting errors, formatter infrastructure failures, and languages that do not format.