feat(oxibadge): cache employee names locally and let readers be a list

Employee names are now cached locally (employees.toml, keyed by reader
index then employee id) instead of being re-fetched from the time
clock on every month: load_employees only asks the device for ids not
already in the cache. When a month has employees the cache doesn't
know yet, a new screen (NewEmployees.svelte) lets the user name them
before continuing to the review screen; the chosen names are local to
Oxibadge only, never written back to the device. The same cache can be
managed afterwards from a drawer reachable from the time clock card in
Settings ("Gestisci dipendenti"), reusing the rename-in-row pattern
from the original mockup.

Settings.readers is a list again (was flattened to a single `reader`
object) so multiple time clocks can be supported later; only the first
one is used today.

Also:
- buildEmployees() now derives the employee list from the month's
  records instead of from every cached name ever seen, so the review
  screen no longer shows employees unrelated to the selected month.
- Renaming an employee from the review screen's pencil button now
  actually persists to the cache (the callback existed but was never
  wired up).
- Translated to English a number of Rust/TS/Svelte comments that had
  been written in Italian; only the i18n locale files should contain
  Italian.
- Minor dedup: extracted PillButton.svelte (was duplicated inline in
  ReaderCard), promoted the repeated .mono CSS rule to app.css, moved
  initials() out of the review feature into $lib/text.ts.

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

oxibadge/src/lib/components/review/TimesheetTable.svelte

@@ -147,10 +147,6 @@
 </div>
 
 <style>
-  .mono {
-    font-family: var(--ox-font-mono);
-  }
-
   .table-box {
     flex: 1;
     min-height: 0;
@@ -249,7 +245,7 @@
     font-size: 13px;
   }
 
-  /* Celle orario */
+  /* Time cells */
   .slot {
     display: flex;
     flex-direction: column;
@@ -356,7 +352,7 @@
     background: rgba(77, 141, 255, 0.12);
   }
 
-  /* Note */
+  /* Notes */
   td.note {
     font-size: 13px;
     color: #6e6e6e;