feat: Major fragmented mp4 optimisation #5030

Job	Run time
Format (Biome)	7s
Format (Cargo)	11s
Lint (Biome)	15s
Detect Changes	6s
Typecheck	1m 19s
Clippy (aarch64-apple-darwin, macos-latest)	2m 17s
Clippy (x86_64-pc-windows-msvc, windows-latest)	3m 44s
Build Desktop	0s
Verify Tauri plugin versions	0s
Rust cache	0s
	7m 59s

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