[feat](trx-config): report unknown configuration keys

Every config struct is #[serde(default)], so a misspelled key was dropped in
silence and the setting kept its default.  Writing `prot = 9999` under
[listen] started the server on 4530 without a word.

Collect the ignored key paths with serde_ignored and pair each with the
closest known key at the same level:

    WARN unknown config key 'listen.prot' (did you mean 'listen.port'?)

Warnings by default, so a config written for a newer version still runs on an
older binary; --strict-config makes them fatal for CI.  Logging now starts
before validation so these warnings are actually visible.

trx-configurator --check drops its hand-maintained key lists and re-implemented
range checks in favour of the real loader and validators, so it no longer
passes configs the binaries reject.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SyX26FCpMQxiBoC7r5K1A7
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-client/src/main.rs

@@ -50,6 +50,9 @@ struct Cli {
     /// Print example configuration and exit
     #[arg(long = "print-config")]
     print_config: bool,
+    /// Treat unknown configuration keys as a fatal error
+    #[arg(long = "strict-config")]
+    strict_config: bool,
     /// Remote server URL (host:port)
     #[arg(short = 'u', long = "url")]
     url: Option<String>,
@@ -135,20 +138,24 @@ async fn async_init() -> DynResult<AppState> {
         std::process::exit(0);
     }
 
-    let (cfg, config_path) = if let Some(ref path) = cli.config {
-        let cfg = ClientConfig::load_from_file(path)?;
-        (cfg, Some(path.clone()))
+    let loaded = if let Some(ref path) = cli.config {
+        ClientConfig::load_from_file(path)?
     } else {
         ClientConfig::load_from_default_paths()?
     };
-    cfg.validate()
-        .map_err(|e| format!("Invalid client configuration: {}", e))?;
+    let config_path = loaded.path.clone();
 
-    init_logging(cfg.general.log_level.as_deref());
+    // Logging comes up before any config complaint so the warnings are visible.
+    init_logging(loaded.config.general.log_level.as_deref());
 
     if let Some(ref path) = config_path {
         info!("Loaded configuration from {}", path.display());
     }
+    loaded.report_unknown_keys(cli.strict_config)?;
+
+    let cfg = loaded.config;
+    cfg.validate()
+        .map_err(|e| format!("Invalid client configuration: {}", e))?;
 
     frontend_runtime.http_auth.tokens = cfg
         .frontends