feat(notes): liens internes, onglet Réseau, living blocks et consentement IA

Rend les liens entre notes visibles et persistants (sync NoteLink au save, auto-save, graphe réseau rafraîchi), ajoute living blocks, Memory Echo, recherche globale, consentement IA explicite et consolide les prototypes design en architectural-grid.

Co-authored-by: Cursor <cursoragent@cursor.com>

memento-note/prisma/migrations/20260524140000_add_note_link/migration.sql

@@ -0,0 +1,26 @@
+-- CreateTable (additive — table may already exist from db push)
+CREATE TABLE IF NOT EXISTS "NoteLink" (
+    "id" TEXT NOT NULL,
+    "sourceNoteId" TEXT NOT NULL,
+    "targetNoteId" TEXT NOT NULL,
+    "contextSnippet" TEXT,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    CONSTRAINT "NoteLink_pkey" PRIMARY KEY ("id")
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS "NoteLink_sourceNoteId_targetNoteId_key" ON "NoteLink"("sourceNoteId", "targetNoteId");
+CREATE INDEX IF NOT EXISTS "NoteLink_sourceNoteId_idx" ON "NoteLink"("sourceNoteId");
+CREATE INDEX IF NOT EXISTS "NoteLink_targetNoteId_idx" ON "NoteLink"("targetNoteId");
+
+DO $$ BEGIN
+  ALTER TABLE "NoteLink" ADD CONSTRAINT "NoteLink_sourceNoteId_fkey" FOREIGN KEY ("sourceNoteId") REFERENCES "Note"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+EXCEPTION
+  WHEN duplicate_object THEN null;
+END $$;
+
+DO $$ BEGIN
+  ALTER TABLE "NoteLink" ADD CONSTRAINT "NoteLink_targetNoteId_fkey" FOREIGN KEY ("targetNoteId") REFERENCES "Note"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+EXCEPTION
+  WHEN duplicate_object THEN null;
+END $$;