100% codec coverage + disc/ and aacs/ module refactors

Codec coverage (DVD + BD + UHD):
- E-AC-3 (Dolby Digital Plus): bsid detection, frame size calc — 8 tests
- DTS-HD MA/HR: extension substream (0x64582025) detection — 8 tests
- LPCM: BD header skip, raw PCM extraction — 6 tests
- DVD VobSub subtitles: passthrough parser — 5 tests
- Dolby Vision: verified RPU NAL type 62 preserved in HEVC — 1 test

Module refactors:
- disc.rs → disc/mod.rs + bluray.rs + dvd.rs + encrypt.rs
- aacs/mod.rs (1661 lines) → mod.rs (21) + keydb.rs + keys.rs + decrypt.rs
- All public APIs preserved, all tests pass

270 tests total, 0 failures.

src/mux/codec/mod.rs

@@ -9,8 +9,10 @@
 
 pub mod ac3;
 pub mod dts;
+pub mod dvdsub;
 pub mod h264;
 pub mod hevc;
+pub mod lpcm;
 pub mod mpeg2;
 pub mod pgs;
 pub mod truehd;
@@ -86,7 +88,8 @@ pub fn parser_for_codec(codec: Codec) -> Box<dyn CodecParser> {
         Codec::DtsHdMa | Codec::DtsHdHr | Codec::Dts => Box::new(dts::DtsParser::new()),
         Codec::TrueHd => Box::new(truehd::TrueHdParser::new()),
         Codec::Pgs => Box::new(pgs::PgsParser::new()),
-        Codec::Lpcm => Box::new(PassthroughParser::new(true)),
+        Codec::Lpcm => Box::new(lpcm::LpcmParser::new()),
+        Codec::DvdSub => Box::new(dvdsub::DvdSubParser::new()),
         _ => Box::new(PassthroughParser::new(true)),
     }
 }