feat: replace Remotion with custom Bradly Engine (Phases 1-3)

- Phase 1: Custom animation engine (interpolate, spring, Easing)
- Phase 2: Custom composition components (AbsoluteFill, Sequence, Img, Video, Audio)
- Phase 3: BradlyPlayer with rAF frame loop, imperative API, controls

Migrated 24 files from remotion/@remotion/player imports to src/engine/.
All type errors from migration resolved. Pre-existing errors remain unchanged.

src/components/ui/PlaybackInfo.tsx

@@ -1,8 +1,8 @@
 import React, { useState, useEffect, useRef } from 'react';
-import { PlayerRef } from '@remotion/player';
+import type { BradlyPlayerRef } from '../../engine/player';
 
 interface PlaybackInfoProps {
-  playerRef: React.RefObject<PlayerRef | null>;
+  playerRef: React.RefObject<BradlyPlayerRef | null>;
   durationInFrames: number;
   fps?: number;
   elementCount?: number;