Initial commit: notification-elements-demo app

Interactive Angular 19 demo for @sda/notification-elements-ui with
6 sections: Bell & Feed, Notification Center, Inbox, Comments &
Threads, Mention Input, and Full-Featured layout. Includes mock
data, dark mode toggle, and real-time event log.

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

node_modules/piscina/dist/abort.d.ts

@@ -0,0 +1,20 @@
+interface AbortSignalEventTargetAddOptions {
+    once: boolean;
+}
+export interface AbortSignalEventTarget {
+    addEventListener: (name: 'abort', listener: () => void, options?: AbortSignalEventTargetAddOptions) => void;
+    removeEventListener: (name: 'abort', listener: () => void) => void;
+    aborted?: boolean;
+    reason?: unknown;
+}
+export interface AbortSignalEventEmitter {
+    off: (name: 'abort', listener: () => void) => void;
+    once: (name: 'abort', listener: () => void) => void;
+}
+export type AbortSignalAny = AbortSignalEventTarget | AbortSignalEventEmitter;
+export declare class AbortError extends Error {
+    constructor(reason?: AbortSignalEventTarget['reason']);
+    get name(): string;
+}
+export declare function onabort(abortSignal: AbortSignalAny, listener: () => void): void;
+export {};