fix: floating webcam preview gets clipped/stuck in HUD passthrough-fallback mode

[Alfredoalv13]

Summary

• The floating webcam preview bubble's drag-clamping logic assumed the HUD overlay window always covers the full screen, using `window.screen.width/height` as a fallback bound.
• That assumption breaks in `getHudOverlayWindowBounds()` (`electron/hudOverlayBounds.ts`): when mouse passthrough isn't supported, the window is deliberately shrunk to a small band anchored to the bottom of the screen (160-540px tall), not full-screen.
• Result: clamping against the full physical screen size let the preview "move" to positions the small window can't actually render into, so it got visually clipped at the window's real edge - looking stuck in roughly the lower 10% of the screen and unable to be repositioned further, exactly as reported.
• Fix: clamp against `window.innerWidth`/`window.innerHeight` directly (the window's actual current size), which is correct in both the full-screen and fallback-band cases.

Test plan

• `tsc --noEmit` clean
• `npm test` - 94/94 files, 819/819 tests passing
• Manual: on a system where HUD mouse passthrough falls back (or by forcing the fallback path), enable the webcam and drag the floating preview to confirm it can move freely within the actual HUD window and isn't clipped