fix: address code-review findings on the 2.16.0 branch

Correctness:
- Recurring writes: move the series DTSTART by the *wall-clock* shift applied
  to the edited occurrence and re-resolve it in the event's zone, instead of by
  a millisecond delta. The old delta baked in whichever UTC offset applied on
  the edited occurrence's date, so pinning a recurring event to another zone —
  or editing an occurrence on the far side of a DST boundary from the series
  anchor — shifted the whole series by an hour. Also snaps the anchor to a UTC
  midnight when the event becomes all-day.
- Detail card and edit form now resolve a pinned zone's abbreviation/offset at
  the *event's* instant, not at "now", so a July event no longer reads
  "CET · 10:00 AM" when opened in January.
- Agenda: the zone used to label multi-day rows now travels on
  AgendaUiState.Success rather than a process-lifetime file-level constant, so
  labelling can't disagree with the grouping after a device time-zone change.
- Week title: spell out the year when the week straddles New Year, via a new
  forceYear flag on formatCalendarTitle.

Performance:
- Build the ~600-entry zone catalogue off the main thread (produceState +
  Dispatchers.Default); resolve the device row's summary on its own so it still
  renders complete on the first frame.
- Pre-normalize each TimeZoneOption's search keys at construction, turning
  ~2400 NFD normalizations per keystroke into plain prefix/substring checks.
  Hoist the combining-mark Regex out of the hot path.
- Key the edit form's local-time line on the fields it reads instead of
  recomputing it on every keystroke.
- Move LauncherNameManager's PackageManager binder calls off the main thread.

Cleanup:
- Drop a duplicate Public icon import and the unused
  event_edit_timezone_clear string.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/main/res/values/strings.xml

@@ -110,7 +110,6 @@
     <string name="event_edit_timezone_recent">Recent</string>
     <string name="event_edit_timezone_all">All time zones</string>
     <string name="event_edit_timezone_none">No time zone matches “%1$s”</string>
-    <string name="event_edit_timezone_clear">Use device zone</string>
     <!-- Shown under the time fields when the event is pinned to another zone:
          the same event expressed where the user actually is. %1$s is a time
          range, e.g. "2:00 PM – 3:00 PM". -->