feat: Add connection timeout options via CLI flags to DIMSE Tools

[karanrane96]

• [app-common] add ConnectionOptions struct with --read-timeout and --write-timeout flags, shared across
  all tools
• [echoscu] add dicom-app-common dependency; add --connect-timeout, --read-timeout, --write-timeout flags
• [findscu] add dicom-app-common dependency; add --connect-timeout, --read-timeout, --write-timeout flags
• [storescu] add --connect-timeout, --read-timeout, --write-timeout flags; wire timeouts in both sync and
  async paths
• [storescp] add --read-timeout, --write-timeout flags (no --connect-timeout — server does not initiate
  TCP connections)

Notes:

• --connect-timeout sets a deadline on TCP connection establishment (TcpStream::connect_timeout),
  preventing indefinite hangs when the remote host is unreachable
• --read-timeout / --write-timeout bound socket I/O, preventing hangs on stalled associations
• All timeout values are in whole seconds