Audit fixes + DVD support foundation (IFO, PS demux, MPEG-2, CSS crack)

Audit fixes (14 critical, 22 warnings):
- UDF: bounds checks on all ICB/FID parsing from disc data
- SCSI Linux: saturating_sub on residual, CDB length guard, buffer size guard
- SCSI macOS: SCSITaskStatus u32 (was u8 — stack corruption)
- AACS: EC mod_inv returns infinity instead of panic, key reduced mod n
- AACS: do_handshake tries all host certs (was returning on first failure)
- H.264: bounds check on SPS < 4 bytes
- ContentReader: error on missing unit key (was zero-fill)
- KEYDB: flat redirect loop (was recursive), 100MB response limit, Windows HOME fallback
- ISO writer: AVDP extent order, partition length, allocation cap
- Network: removed TCP_NODELAY on bulk stream
- MKV: guard on u64::MAX seek
- disc.rs: saturating_sub on extent offset, simplified dead region code
- cargo fmt (610 violations), cargo clippy --fix (55 auto-fixes)

DVD support (new files):
- src/ifo.rs — IFO parser (VIDEO_TS.IFO, VTS_XX_0.IFO, PGC chains, cells, streams) — 13 tests
- src/mux/ps.rs — MPEG-2 Program Stream demuxer (pack headers, PES, private stream 1) — 12 tests
- src/mux/codec/mpeg2.rs — MPEG-2 video parser (sequence headers, I-frame detection) — 15 tests
- src/css/crack.rs — split-attack algorithm (LFSR cipher needs verification — test ignored)

226 tests total (was 186), 1 ignored (CSS crack needs cipher verification).

src/mux/codec/mod.rs

@@ -8,15 +8,16 @@
 //! - Convert PTS from 90kHz to nanoseconds
 
 pub mod ac3;
+pub mod dts;
 pub mod h264;
 pub mod hevc;
-pub mod vc1;
-pub mod dts;
-pub mod truehd;
+pub mod mpeg2;
 pub mod pgs;
+pub mod truehd;
+pub mod vc1;
 
-use crate::disc::Codec;
 use super::ts::PesPacket;
+use crate::disc::Codec;
 
 /// A single frame ready for MKV muxing.
 pub struct Frame {
@@ -53,7 +54,9 @@ pub struct PassthroughParser {
 
 impl PassthroughParser {
     pub fn new(always_keyframe: bool) -> Self {
-        Self { keyframe: always_keyframe }
+        Self {
+            keyframe: always_keyframe,
+        }
     }
 }
 
@@ -77,6 +80,7 @@ pub fn parser_for_codec(codec: Codec) -> Box<dyn CodecParser> {
     match codec {
         Codec::H264 => Box::new(h264::H264Parser::new()),
         Codec::Hevc => Box::new(hevc::HevcParser::new()),
+        Codec::Mpeg2 => Box::new(mpeg2::Mpeg2Parser::new()),
         Codec::Vc1 => Box::new(vc1::Vc1Parser::new()),
         Codec::Ac3 | Codec::Ac3Plus => Box::new(ac3::Ac3Parser::new()),
         Codec::DtsHdMa | Codec::DtsHdHr | Codec::Dts => Box::new(dts::DtsParser::new()),