smbserver: add SMB 3.1.1 dialect support

[n3rada]

Hello maintainers 👋

Closes #1981.
Closes #1829.

smbserver.py only negotiated SMB 2.0.2 regardless of what the client offered. This PR adds real SMB 3.1.1 support on the server side.

What this PR does:

• Dialect selection: the server now picks the best common dialect from what the client offers (0x0311 > 0x0210 > 0x0202). When an SMB1 negotiate arrives with SMB 2.???, the server responds with the wildcard dialect so the client sends a proper SMB2 negotiate, which can then land on 3.1.1.

• Negotiate contexts: for dialect 3.1.1 the server appends SMB2_PREAUTH_INTEGRITY_CAPABILITIES (SHA-512, no salt) and SMB2_ENCRYPTION_CAPABILITIES (AES-128-GCM preferred, AES-128-CCM fallback) to the negotiate response.

• Pre-authentication integrity hash: the server maintains a connection-level pre-auth hash across the negotiate exchange and forks it into a session-level hash at session setup, updating it with each request/response pair.

• Signing key derivation: once authentication succeeds the raw session key is replaced by the SP 800-108 counter-mode KBKDF output (label="SMBSigningKey\x00", context=session pre-auth hash, L=128).

• AES-CMAC signing: a new signSMBv3 method signs outgoing packets with AES-CMAC instead of HMAC-SHA256, as required for the SMB 3.x dialect family.

• Session encryption: when the client offers encryption ciphers, the server derives SessionEncryptionKey and SessionDecryptionKey via KBKDF, sets SMB2_SESSION_FLAG_ENCRYPT_DATA in the session setup response, and wraps all subsequent traffic in SMB2_TRANSFORM_HEADER (AES-128-GCM or AES-128-CCM). Incoming encrypted packets are decrypted before processing.

The validateNegotiateInfo response now echoes back the negotiated dialect instead of always returning 0x0202.

Best regards

[n3rada]

This PR also fixes #1829.

processRequest was setting respPacket['SessionID'] = connData['Uid'] for all SMB2 responses. smb2Logoff zeroes connData['Uid'] before returning, so the LOGOFF response was always sent with SessionID=0.

SESSION_SETUP assigns a new SessionId; all other commands must echo the SessionId from the request. The fix applies exactly that rule:

if packet['Command'] == smb2.SMB2_SESSION_SETUP:
    respPacket['SessionID'] = connData['Uid']
else:
    respPacket['SessionID'] = packet['SessionID']