fix(hover-card): maiden name false positive, placeholder on non-empty editor, card persistence

- PersonHoverCard: alias is compared against both `lastName` and `displayName`
  before showing as maiden name — prevents false positive when alias is stored
  as the full current name (e.g. "Maria Schmidt" ≠ "Schmidt" but name unchanged)
- PersonMentionEditor: data-placeholder was set statically so the CSS ::before
  rule showed the placeholder on any blur even with content; now a $effect
  toggles the attribute based on editor.isEmpty
- TranscriptionReadView: hovering onto the card itself cancels the 150ms close
  timer so the card stays open while reading it; leaving the card closes it
  immediately — onmouseenter/onmouseleave wired through PersonHoverCard props
- hoverCardPosition: removed scrollX/scrollY offset since the card is now
  position:fixed (scroll is already baked into getBoundingClientRect coords)
- MentionDropdown: raised z-index from z-20 to z-50 to render above the hover card
- vite.config.ts: pre-bundle Tiptap packages to avoid HMR waterfall on first load

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/components/MentionDropdown.svelte

@@ -111,7 +111,7 @@ function selectItem(item: Person) {
 	unauthenticated users.
 -->
 <div
-	class="fixed z-20 w-72 overflow-hidden rounded-sm border border-line bg-surface shadow-lg"
+	class="fixed z-50 w-72 overflow-hidden rounded-sm border border-line bg-surface shadow-lg"
 	role="listbox"
 	aria-label={m.person_mention_btn_label()}
 	style:top={position.top}