feat: add session library backend APIs

Add persisted session and pattern metadata for pinning, archiving, manual titles, and favorite patterns. Expose backend query and mutation APIs for session library features, and cover the shared helpers with tests.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/shared/domain/pattern.ts

@@ -31,6 +31,7 @@ export interface PatternDefinition {
   id: string;
   name: string;
   description: string;
+  isFavorite?: boolean;
   mode: OrchestrationMode;
   availability: PatternAvailability;
   unavailabilityReason?: string;