feat: initial implementation of Focus RSVP speed reader

- Pure frontend SPA (Vite + React 19 + TypeScript + Tailwind CSS v4)
- Spritz ORP engine with absolute center crosshair gaze fixation
- Multilingual hybrid segmentation via Intl.Segmenter with punctuation attachment
- Adaptive breathing rhythm delay algorithm for natural comprehension
- IndexedDB local bookshelf, progress persistence, and client-side EPUB/TXT/MD parsing
- Curated sci-fi, philosophy, and classic speech samples
- Dark/OLED/Sepia/Slate/Nord themes and rich keyboard controls

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

src/index.css

@@ -0,0 +1,71 @@
+@import "tailwindcss";
+
+@layer base {
+  html, body, #root {
+    height: 100%;
+    margin: 0;
+    padding: 0;
+    -webkit-font-smoothing: antialiased;
+    -moz-osx-font-smoothing: grayscale;
+    user-select: none;
+  }
+}
+
+/* Custom theme container classes */
+.theme-oled {
+  background-color: #000000;
+  color: #f4f4f5;
+  color-scheme: dark;
+}
+
+.theme-dark {
+  background-color: #09090b;
+  color: #f4f4f5;
+  color-scheme: dark;
+}
+
+.theme-slate {
+  background-color: #0f172a;
+  color: #f1f5f9;
+  color-scheme: dark;
+}
+
+.theme-nord {
+  background-color: #242933;
+  color: #eceff4;
+  color-scheme: dark;
+}
+
+.theme-sepia {
+  background-color: #fbf0d9;
+  color: #433422;
+  color-scheme: light;
+}
+
+.theme-paper {
+  background-color: #ffffff;
+  color: #18181b;
+  color-scheme: light;
+}
+
+/* Range input thumb styling */
+input[type="range"]::-webkit-slider-thumb {
+  -webkit-appearance: none;
+  appearance: none;
+  width: 14px;
+  height: 14px;
+  border-radius: 9999px;
+  background-color: #f43f5e;
+  cursor: pointer;
+  box-shadow: 0 0 6px rgba(244, 63, 94, 0.4);
+}
+
+input[type="range"]::-moz-range-thumb {
+  width: 14px;
+  height: 14px;
+  border-radius: 9999px;
+  background-color: #f43f5e;
+  border: none;
+  cursor: pointer;
+  box-shadow: 0 0 6px rgba(244, 63, 94, 0.4);
+}