Repeat scroll actions in Mouse scanning

[enaboapps]

Closes #870.

Change

• Mouse scanning's scroll tiles issue one immediate five-unit step and repeat at the saved Scroll interval when Repeat mouse movement and scrolling is enabled.
• The next local or Remote switch press stops scrolling, consumes its release, and restarts the Mouse panel at its first row. With repeat disabled, scrolling remains a single step.
• The mouse ring shows persistent scroll feedback throughout repeat. Repeat state clears on failure, stop, mode or display change, and shutdown. Existing Remote behavior and saved settings schemas remain unchanged.
• The Mouse settings label and scanning help explain the shared repeat control.

Validation

• npm run lint — pass
• npm test — pass (223 UI tests, 5 update-feed tests)
• npm run build — pass
• cargo fmt --manifest-path src-tauri/Cargo.toml --check — pass
• cargo clippy --manifest-path src-tauri/Cargo.toml --all-targets -- -D warnings — pass
• cargo test --manifest-path src-tauri/Cargo.toml — pass (526 Rust unit tests, 7 integration tests; 1 ignored)
• Windows 11 Parallels VM: built native ARM64 debug executable from head c50678e7b65a836f506bbe6bf345049d7d4bc899 using Node 24 and Rust 1.97.1. Assigned Space/Enter/Backspace/F9 as local switch keys, opened Mouse with F9, selected Scroll up through the scanned panel, and observed the active scroll prompt and arrow ring while Notepad moved from around line 278 to line 150 over three seconds with a 500 ms repeat interval. A Space press returned the panel to its first row and restored the idle ring. With repeat disabled, Scroll down moved Notepad once; the view remained stable two seconds later. Notepad remained the foreground window while the overlays were visible. Original VM settings were restored after testing.
• VM limit: switch presses were generated as keyboard events through the Windows local switch hook; a separate hardware switch was not connected.
• Independent review of the latest head found no remaining actionable issues. Its earlier finding about short-lived scroll feedback was fixed and re-reviewed.