Filter noisy internal warnings from boringtun and iroh net_report

The CLI's default tracing filter previously allowed WARN level logs from
boringtun and iroh, producing two confusing and noisy log messages during
routine operation:
1. 'WARN HANDSHAKE(REJECT_AFTER_TIME - KEEPALIVE_TIMEOUT - REKEY_TIMEOUT (on receive))':
   emitted by boringtun's internal timer tick when an endpoint primarily
   receives data for 165 seconds (180s - 10s - 5s). In boringtun, this is a
   routine scheduled rekey timer rather than an error or failure, but was
   unhelpfully logged as warn! upstream.
2. 'WARN probe timed out':
   emitted by iroh's net_report module during background HTTP captive portal
   detection when running in isolated subnets or VMs without direct internet
   access. This probe has no impact on mesh connectivity.

Update the default logging filter to:
  'info,iroh=warn,iroh::net_report=error,quinn=warn,rustls=warn,boringtun=error,mainline=off'

Real WireGuard handshake and rekey failures continue to be detected and
reported cleanly by Tsunagi's own data plane diagnostics and automatic
fallback handlers at INFO and WARN levels.

Validation on Linux:
- cargo fmt --all -- --check passed.
- cargo clippy --locked --workspace --all-targets -- -D warnings passed.
- cargo test --locked --workspace --all-targets passed.
- cargo build --release passed.

crates/tsunagi-cli/src/main.rs

@@ -702,7 +702,7 @@ fn main() -> std::process::ExitCode {
         .or_else(|| std::env::var("TSUNAGI_LOG").ok())
         .or_else(|| std::env::var("RUST_LOG").ok())
         .unwrap_or_else(|| {
-            "info,iroh=warn,quinn=warn,rustls=warn,boringtun=warn,mainline=off".to_string()
+            "info,iroh=warn,iroh::net_report=error,quinn=warn,rustls=warn,boringtun=error,mainline=off".to_string()
         });
 
     let is_debug = log_filter.contains("debug") || log_filter.contains("trace");