fix: resolve all 69 ESLint warnings across 40 files

- Remove unused imports (Mail, CalendarIcon, Plus, Circle, cn, Link,
  MessageCircle, User, Tag, FolderUp, useEffect, LogOut, GripVertical,
  Check, X, HoverActionsMode, HoverActionsCorner, asn1js, Convert, etc.)
- Prefix unused variables/params with underscore to satisfy no-unused-vars
- Add missing React hook dependencies (exhaustive-deps)
- Wrap handleNavigateUp in useCallback and selectedGroupMembers in useMemo
- Remove unused eslint-disable directives in jmap/client.ts
- Replace as any with typed casts in filter-store and smime-store tests
- Remove dead code (macOk assignment, unused now variable)

app/api/dev-jmap/[...path]/route.ts

@@ -89,7 +89,7 @@ function localDateTime(dayOffset: number, hour: number, minute: number): string
 }
 
 /** Parse a JMAP duration like "PT1H30M", "P1D", "PT45M" into milliseconds. */
-function parseDurationMs(dur: string): number {
+function _parseDurationMs(dur: string): number {
   let ms = 0;
   const dayMatch = dur.match(/(\d+)D/);
   const hourMatch = dur.match(/(\d+)H/);