v1.2.0: Add 4 new protocols, fix 5 existing, port Kia V6 encoder

New protocols (from ProtoPirate):
- Mazda V0: 433MHz, pair-based decoding, XOR deobfuscation
- Mitsubishi V0: 868MHz, PWM, bit negation + XOR unscrambling
- Porsche Touareg: 433/868MHz, sync preamble, 24-bit rotate cipher
- Fiat V1 (Magneti Marelli BSI): 433MHz, auto-detected timing variants

Protocol fixes aligned with ProtoPirate reference:
- Kia V1: Fix Manchester level mapping (inverted convention), off-by-one
  bit count, CRC4 simplified to 7 bytes + offset 1
- Kia V2: Fix CRC byte layout (was double-counting nibbles), off-by-one
  bit count, preamble short-HIGH handling
- Fiat V0: Fix endbyte transform (remove (<<1)|1), standard Manchester
  encoder (was differential), 7 btn bits (was 6), gap path fallback
- PSA: Fix modified TEA (XTEA-like dynamic key selection), XOR decrypt
  byte mapping, critical key2_low construction bug, encoder polarity and
  preamble, add key1_high nibble validation, dual preamble patterns
- Ford V0: Add calculate_checksum (sums all serial+count bytes) for encoder

Kia V6 encoder ported:
- Forward AES-128 (SubBytes, ShiftRows, MixColumns, encrypt)
- encrypt_payload: build plaintext, AES encrypt, pack into 3 parts
- Two-pass Manchester upload (640 + 38 preamble pairs)
- fx_field extraction stored in DecodedSignal.extra for encode roundtrip

Updated README, protocol docs, and version bump to 1.2.0.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "kat"
-version = "1.1.3"
+version = "1.2.0"
 edition = "2021"
 description = "Keyfob Analysis Toolkit - HackRF/RTL-SDR signal capture, decode, and transmit (HackRF only)"
 authors = ["KAT Team"]