feat: non-destructive sync, vocabulary import, simple template syntax, and improved error handling

[nithou]

Summary

• Non-destructive sync: Re-importing highlights no longer overwrites user content. A ## Personal
  Notes section is preserved across re-imports. Users can position it anywhere in their template.
• Vocabulary import (My Words): Extracts looked-up words from Kobo's WordList table into a single
  vocabulary file. Dynamically detects available columns (DictSuffix, VolumeId, DateCreated) via PRAGMA
  table_info, following the existing hasBookmarkColorColumn() pattern. Controlled by two new settings:
  "Import vocabulary" and "Vocabulary file name".
• Simple template syntax: Supports {{Title}}, {{Author}}, {{highlights}} and other shorthand
  variables as an alternative to Eta <%= it.bookDetails.title %> syntax. Both syntaxes can be mixed
  freely. Tolerant of linter-inserted spaces ({{ Title }}, { { Title } }).
• Better error handling: Replaces the generic "Something went wrong... Check console" notice with
  specific, actionable messages. An ImportContext class tracks books imported, highlights extracted,
  vocabulary words, and warnings, presenting a summary like "Imported 12 books (347 highlights). 2
  warnings: ...".
• Remember SQLite path (from feat: remember KoboReader.sqlite path between sessions #521 by @eton-s): Saves the KoboReader.sqlite filesystem path between
  sessions using Electron's webUtils.getPathForFile. Auto-loads on next modal open.
• Handle missing bookTitle (from fix: handle missing bookTitle for custom books #483 by @dulangaj): Uses content.title as fallback instead of
  throwing when bookTitle is null, making the plugin resilient to custom books/articles with incomplete
  metadata.

Additional fixes

• Fix broken click/mouseover handlers in suggestion dropdown (.bind() result was discarded, never called)
• Fix ReadStatus.Unopened (0) rendering as "Unknown" due to falsy check
• Await saveSettings() consistently in all settings onChange handlers
• Remove async from all synchronous sql.js Repository methods and cascade through HighlightService
• Replace SELECT DISTINCT with GROUP BY Title in getAllBookDetails() for deterministic deduplication
• Fix DOM element creation order in modal; replace innerHTML with safe appendText/createEl
• Remove blanket eslint-disable no-unused-vars from Suggest.ts
• Fix typo "progess" → "progress" in settings
• Remove unused moment dependency; move @types/better-sqlite3, esbuild-plugin-wat, @popperjs/core to devDependencies
• Make repository tests database-agnostic (no longer hardcoded to specific book data)