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/lib/locales/en.json

@@ -10,13 +10,6 @@
       "idle": "Test connection",
       "testing": "Connecting...",
       "retry": "Retry"
-    },
-    "error_title": "Could not reach the time clock",
-    "errors": {
-      "connection-refused": "Connection refused",
-      "timed-out": "Connection timed out",
-      "dns-failure": "Invalid or unreachable address",
-      "unknown": "Connection error"
     }
   },
   "confirm_month": {
@@ -38,6 +31,9 @@
     "title": "Fetching employees...",
     "description": "Reading the employee names registered on the time clock. Just a moment."
   },
+  "errors": {
+    "title": "Could not reach the time clock"
+  },
   "done": {
     "message": "Nothing to do here."
   }