feat: add Syslog TCP Provider

[alpar]

Summary

Adds a new Syslog TCP Provider that listens for syslog messages on a configurable TCP port and processes them as Keep alerts.

Closes #1750

Features

• Listens on configurable host/port (default: 0.0.0.0:514)
• Supports RFC 3164 (BSD) and RFC 5424 syslog message formats
• Parses syslog priority into facility and severity
• Maps syslog severity to Keep alert severity levels
• Graceful fallback for malformed/non-standard messages
• Consumer pattern with start_consume()/stop_consume() (same as Kafka provider)
• Full test coverage for parsing, severity mapping, and TCP handling

Usage

Configure the provider with host and port:

providers:
  - type: syslog
    authentication:
      host: 0.0.0.0
      port: 514

Then configure your syslog sources (e.g., vCenter, network devices) to forward to Keep on the configured port.

Alert Fields

Each syslog message is pushed as an alert with:

• name: app-name - message[:50]
• message: full syslog message
• severity: mapped from syslog severity
• syslog_facility, syslog_severity, syslog_hostname, syslog_app_name, syslog_pid, syslog_timestamp

Severity Mapping

Syslog	Keep
Emergency/Alert/Critical	critical
Error	high
Warning	warning
Notice/Informational	info
Debug	low

[CLAassistant]

All committers have signed the CLA.

[alpar]

Hi @shahargl, gentle ping — CI is green and ready for review. Thanks!

[alpar]

Hi @shahargl @tb0x, second ping — CI green for 7 days. This adds a Syslog TCP provider for receiving syslog messages as alerts. Ready for review. 🙏