fix(oxibadge): show connection errors instead of failing silently

load_records/load_employees failures were only logged to the console
and silently reset the UI to the month picker. Errors now flow through
a shared store (src/lib/error.ts) into an ErrorBanner, reused by both
Onboarding and ConfirmMonth, with the raw message passed straight
through from Rust (no stable-code classification layer — these are
mostly plain I/O errors, not worth categorizing).

i18n stays grouped per screen as before, with error-related strings
split into their own top-level "errors" group.

Assisted-by: Claude Sonnet 5 <noreply@anthropic.com>

oxibadge/src-tauri/src/lib.rs

@@ -22,27 +22,15 @@ async fn test_connection(host: String, port: u16) -> Result<(), String> {
     connect_with_retries(&host, port).await.map(|_| ())
 }
 
-/// Connects to the device, trying up to 3 times, returning a stable error
-/// code (not a user-facing message) on failure so the frontend can
-/// translate it.
+/// Connects to the device, trying up to 3 times, returning the last error
+/// message as-is on failure.
 async fn connect_with_retries(host: &str, port: u16) -> Result<R701, String> {
     let mut last_error = String::new();
     for _ in 0..3 {
-        let err = match R701::connect((host, port)).await {
+        match R701::connect((host, port)).await {
             Ok(r701) => return Ok(r701),
-            Err(err) => err,
-        };
-        last_error = match err.kind() {
-            std::io::ErrorKind::ConnectionRefused => "connection-refused".to_string(),
-            std::io::ErrorKind::TimedOut => "timed-out".to_string(),
-            _ if err
-                .to_string()
-                .contains("failed to lookup address information") =>
-            {
-                "dns-failure".to_string()
-            }
-            _ => "unknown".to_string(),
-        };
+            Err(err) => last_error = err.to_string(),
+        }
     }
     Err(last_error)
 }