Initial commit: timeline-elements-ui library

Angular 19 component library for timelines and event tracking:
timeline, Gantt chart, event cards, date markers, connectors,
and custom event templates. Includes signal-based services,
SCSS design tokens with dark mode, and TypeScript type definitions.

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

build-for-dev.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+set -e
+
+echo "Building @sda/timeline-elements-ui for local development..."
+npm run build
+cd dist
+npm pack
+echo "Done! Package is ready in dist/"