Appenders: network and transport

- 2fb4539f time out writes to stalled TelnetAppender clients
- 15d16eed add a listen address to TelnetAppender
- bd35fe0d add a TransportSecurity option to the MailKit SmtpAppender

Appenders: syslog record integrity

- eccb876e escape NUL characters in LocalSyslogAppender messages
- 46582e52 report a RemoteSyslogAppender Identity that would split the record
- 360a1026 fix the lifetime of the LocalSyslogAppender identity

AdoNet appender

- 9f5c9557 contain per-event failures in AdoNetAppender.SendBuffer
- 19fdb4a2 warn when AdoNetAppender executes layout-generated SQL
- e80b3810 redact the password when reporting a failed database connection

Reliability and resource bounds

- 3fd97cb5 bound the waits for the file locking mutexes
- 394fd3dc bound regular expression matching in the string match filters
- 86ecb152 flush TextWriterAppender under the appender lock
- 1786b139 keep the impersonated user name when a logging event is fixed

Diagnostics

- ecd1b8b9 report the first appender error without log4net.Internal.Debug

Build and release infrastructure

- 9cc34d29 make the release verification scripts fail closed
- 28d411a5 pin the Maven wrapper and distribution downloads
- e203b7c7 remove the git-broadcast workflow

Documentation

- 6bc3df34 document that configuration is trusted input
- 287fa9cd document that format strings are trusted developer input
- dc17e1ba document the conventions the security scan work relied on (#309)

Notes for reviewers

Several commits introduce secure defaults with a named opt-out (SendTimeoutMillis, MatchTimeoutMillis, LockTimeoutMillis); those are behaviour changes on upgrade and are recorded in the changelog. The documentation commits deliberately settle recurring reports in the threat model rather than changing code.