fix: Phase 2 QA — all 25 remaining HIGH/MEDIUM/LOW issues

HIGH fixes (7):
- H1: VNCdirectory admin i18n — 30+ translation keys added
- H2: handleSave try/catch with error toast
- H3: Free/busy accountId scoping
- H4: cancelEventBookings filter by eventId
- H5: Resource picker static apiFetch import
- H6: Sharing-store toast messages via lastMessage state
- H7: roleLabel for all resource types

MEDIUM fixes (11):
- M1: identitySignatureMap cleanup on delete
- M2: Now-line relative positioning
- M3: Radial menu disabled item keyboard nav
- M4: Radial menu stable event listener via refs
- M5: cancelBooking error on missing booking
- M6: PasswordRow isMasked state flag
- M7: Extract shared rights into lib/sharing-rights.ts
- M8: VNCtalk client server-side guard
- M9: Collabora configManager instead of process.env
- M10: CONFIG_ENV_MAP VNCdirectory fields
- M11: SENSITIVE_CONFIG_KEYS field name unification

LOW fixes (7):
- L1-L3: Unused imports removed
- L4: aria-labels on close, clear, search, spinner
- L5-L7: Comments for intentional patterns, null guard

components/settings/import-settings.tsx

@@ -2,7 +2,7 @@
 
 import { useState, useRef, useCallback, useEffect } from "react";
 import { useTranslations } from "next-intl";
-import { Upload, FolderOpen, Download, AlertTriangle, Check, X } from "lucide-react";
+import { Upload, AlertTriangle, Check, X } from "lucide-react";
 import { Button } from "@/components/ui/button";
 import { SettingsSection, SettingItem, RadioGroup, Select } from "./settings-section";
 import { importEmails, type ConflictResolution, type ImportProgress, type ImportResult } from "@/lib/email-import";
@@ -128,7 +128,7 @@ export function ImportSettings() {
               : t("choose_files")}
           </Button>
           {files.length > 0 && !importing && (
-            <Button variant="ghost" size="sm" onClick={reset}>
+            <Button variant="ghost" size="sm" onClick={reset} aria-label="Clear selection">
               <X className="w-4 h-4" />
             </Button>
           )}

components/settings/signature-editor-modal.tsx

@@ -184,7 +184,7 @@ export function SignatureEditorModal({
           <h2 className="text-lg font-semibold text-foreground">
             {isEditing ? t('edit_signature') : t('new_signature')}
           </h2>
-          <Button variant="ghost" size="icon" onClick={onClose} className="h-8 w-8">
+          <Button variant="ghost" size="icon" onClick={onClose} className="h-8 w-8" aria-label="Close">
             <X className="w-4 h-4" />
           </Button>
         </div>