refactor: split package.rs, mod.rs, listener.rs, and lnd.rs into focused submodules
- R35: Split package.rs (1794 lines) into package/{mod,config,validation,lifecycle}.rs
- R36: Split mesh/listener.rs (1799 lines) into listener/{mod,session,frames,decode,dispatch,bitcoin}.rs
- R37: Split rpc/mod.rs into mod.rs + dispatcher.rs, middleware.rs, response.rs (54% reduction)
- R38: Split lnd.rs (1064 lines) into lnd/{mod,info,channels,wallet,payments}.rs
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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