impl learnings and add configuration options

[rustonbsd]

• implementing learnings from https://github.com/Podcastindex-org/podping.alpha/commits/master/dtt-fork
• updated actor-helper
• making merge strategies and params configurable

Summary by CodeRabbit

• Chores

  • CI: removed PR "edited" trigger; checkout action updated. Crate bumped to v0.3.0.

• New Features

  • Centralized builder-based Config API and new TopicId type. Multiple new and updated examples showing full configuration.

• Refactor

  • Background components converted to cancellable spawned tasks with configurable intervals, jitter, and improved lifecycle handling.

• Bug Fixes

  • Stronger DHT retry/timeout behavior, safer publish semantics, bounded message history, improved record validation, join/merge stability and clearer logging.

• Tests

  • Added integration and cancellation tests; updated unit tests.

• Documentation

  • README, ARCHITECTURE, and PROTOCOL revised with upgrade/migration guidance.