perf(camera): avoid resizing canvas and re-querying context on every video frame

[Rohit-rk07]

Summary

doUseCamera redraws camera frames every 100ms and currently performs canvas resize + context lookup on each frame.

Code references

• js/utils/utils.js in draw():
  • canvas.width = w;
  • canvas.height = h;
  • canvas.getContext(2d).drawImage(video, 0, 0, w, h);

Why this matters

• Setting canvas.width/height each frame resets the drawing buffer/state and is expensive.
• Re-fetching getContext(2d) every frame adds avoidable overhead.
• Combined with periodic capture this increases CPU use, especially on low-power devices.

Expected behavior

• Set canvas.width/height once during camera/session setup (or only when dimensions change).
• Cache the 2D context once and reuse it in the frame loop.

Suggested fix

Move canvas sizing and context initialization outside draw() and keep draw() limited to drawImage + export logic.