Raw DER signature with SIGHASH_ALL appended

Commits to:
✓ All inputs (their outpoints/txid:vout references)
✓ All input sequences
✓ All outputs (values and scripts)
✓ Transaction version
✓ Transaction locktime

Does NOT commit to:
✗ Input amounts (in legacy; SegWit/Taproot DO commit to amounts)
✗ Input scriptPubKeys (in legacy; Taproot DOES commit to scriptPubKeys)

Transaction:
├── Version (4 bytes)
├── Inputs [committed]
│   ├── Input 0: txid + vout + scriptSig + sequence
│   ├── Input 1: txid + vout + scriptSig + sequence
│   └── ...
├── Outputs [committed]
│   ├── Output 0: value + scriptPubKey
│   ├── Output 1: value + scriptPubKey
│   └── ...
└── Locktime (4 bytes)

All of this is captured in the sighash preimage and signed.

# Raw DER signature with SIGHASH_ALL appended
# Format: <DER prefix> <r> <s> <sighash_type>
30 44
  02 20 <r: 32 bytes>
  02 20 <s: 32 bytes>
01  ← SIGHASH_ALL type byte

# Full scriptSig in P2PKH transaction
<sig_with_sighash_all> <pubkey>

# Hex example (71-byte SIGHASH_ALL signature):
3044022045... (69 bytes DER) + 01 (sighash type) = 70 bytes total

# Creating a SIGHASH_ALL signature
def sign_input_sighash_all(private_key, tx, input_index, script_code):
    # Compute the sighash
    z = get_signature_hash(tx, input_index, script_code, SIGHASH_ALL)

    # Sign with ECDSA
    r, s = ecdsa_sign(private_key, z)

    # Encode as DER
    der_sig = encode_der(r, s)

    # Append sighash type byte
    return der_sig + bytes([SIGHASH_ALL])