Initial commit: notification-elements-ui library

Angular 19 component library for notifications & communication:
- ntf-bell: notification bell with badge count and shake animation
- ntf-feed / ntf-feed-item: real-time notification feed with grouping
- ntf-center: full notification center with category filter tabs
- ntf-inbox / ntf-inbox-item: two-column inbox with search and detail
- ntf-comment / ntf-thread: comment threads with replies and reactions
- ntf-mention-input: text input with @mention autocomplete
- ntf-empty-state: empty state placeholder
- ntf-item-def: custom template directive for notification items

Includes signal-based services, SCSS design tokens with dark mode,
utility functions, and full TypeScript type definitions.

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

tsconfig.json

@@ -0,0 +1,28 @@
+{
+  "compileOnSave": false,
+  "compilerOptions": {
+    "outDir": "./dist/out-tsc",
+    "strict": true,
+    "noImplicitOverride": true,
+    "noPropertyAccessFromIndexSignature": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
+    "skipLibCheck": true,
+    "esModuleInterop": true,
+    "sourceMap": true,
+    "declaration": true,
+    "experimentalDecorators": true,
+    "moduleResolution": "bundler",
+    "importHelpers": true,
+    "target": "ES2022",
+    "module": "ES2022",
+    "lib": ["ES2022", "dom"],
+    "useDefineForClassFields": false
+  },
+  "angularCompilerOptions": {
+    "enableI18nLegacyMessageIdFormat": false,
+    "strictInjectionParameters": true,
+    "strictInputAccessModifiers": true,
+    "strictTemplates": true
+  }
+}