Give the drag animation its own base frame size

The shared FRAME_SCALE has to stay under 0.5 so the corners animation can
fit two frames side by side, but nothing else is on screen while the drag
animation runs, so it can afford a roomier frame.

frameSize() now takes the scale as an argument; drag passes
DRAG_FRAME_SCALE and the min/max resize multipliers apply on top of it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Tg15tLAuT6NrCE1ZxKVgDB

server/index.js

@@ -15,6 +15,7 @@ import {
   BOUNCE_SPEED,
   CORNER_INTERVAL_SECONDS,
   CORNER_MARGIN,
+  DRAG_FRAME_SCALE,
   DRAG_MIN_SCALE,
   DRAG_MAX_SCALE,
   BACKGROUNDS,
@@ -47,6 +48,7 @@ app.get('/config.js', (_req, res) => {
       `export const BOUNCE_SPEED = ${BOUNCE_SPEED};\n` +
       `export const CORNER_INTERVAL_SECONDS = ${CORNER_INTERVAL_SECONDS};\n` +
       `export const CORNER_MARGIN = ${CORNER_MARGIN};\n` +
+      `export const DRAG_FRAME_SCALE = ${DRAG_FRAME_SCALE};\n` +
       `export const DRAG_MIN_SCALE = ${DRAG_MIN_SCALE};\n` +
       `export const DRAG_MAX_SCALE = ${DRAG_MAX_SCALE};\n` +
       `export const BACKGROUNDS = ${JSON.stringify(BACKGROUNDS)};\n` +