fix(tsc): 0 erreur TypeScript — toutes les 31 erreurs résolues

Types:
- NoteType: 'daily' ajouté
- PROPERTY_TYPES: 'relation' ajouté
- SlashItem: isFavorite? ajouté
- SuggestChartsResponse: error? ajouté

Fixes propres:
- import/route: Date | null → ?? undefined (3 occ)
- notes/route: JSON.stringify sur checkItems/labels
- user/export: b.title → b.seedIdea, Buffer → Uint8Array
- study-plan: language column inexistante → défaut 'fr'
- notebooks/[id]: parentId → parent connect/disconnect
- brainstorm convert/finalize:  async callback
- next.config: @ts-expect-error inutile supprimé
- ai-settings: revalidateTag(tag, 'default')

Casts (TipTap/Prisma, safe at runtime):
- tiptap-chart/math extensions: InputRule/options as any
- chat/route: system messages as any
- note-graph-view: ForceGraph2D as any
- property-value-editor: relation comparison
- sanitize-content: TrustedHTML cast

memento-note/lib/sanitize-content.ts

@@ -20,7 +20,7 @@ const SVG_SANITIZE_CONFIG = {
 
 export function sanitizeIllustrationSvg(svg: string): string {
   if (!svg) return ''
-  return DOMPurify.sanitize(svg, SVG_SANITIZE_CONFIG)
+  return DOMPurify.sanitize(svg, SVG_SANITIZE_CONFIG as any) as unknown as string
 }
 
 export function sanitizeRichHtml(html: string): string {