Observer platform redesign Phase 4: migrate charts to Tremor, redesign all pages

- Migrate 9 chart components from Nivo to @tremor/react (BarChart, AreaChart, DonutChart, ScatterChart)
- Remove @nivo/*, @react-spring/web dependencies (45 packages removed)
- Redesign dashboard: 6 stat tiles, competition pipeline, score distribution, juror workload, activity feed
- Add new /observer/projects page with search, filters, sorting, pagination, CSV export
- Restructure reports page from 5 tabs to 3 (Progress, Jurors, Scores & Analytics) with per-tab CSV export
- Redesign project detail: breadcrumb nav, score card header, 3-tab layout (Overview/Evaluations/Files)
- Update loading skeletons to match new layouts

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

tailwind.config.ts

@@ -6,6 +6,7 @@ const config: Config = {
     './src/pages/**/*.{js,ts,jsx,tsx,mdx}',
     './src/components/**/*.{js,ts,jsx,tsx,mdx}',
     './src/app/**/*.{js,ts,jsx,tsx,mdx}',
+    './node_modules/@tremor/**/*.{js,ts,jsx,tsx}',
   ],
   theme: {
     container: {