feat: design system v2 with liquid glass aesthetic

Overhaul design constants for OLED-first dark mode:
- Colors: brand palette, phase colors, glass/shadow tokens, gradients
- Typography: Inter font scale matching iOS type system
- Spacing: 4px base unit with layout constants
- Border radius: liquid glass card radii
- Animations: spring/timing presets for UI transitions

Add v2 product docs (PRD, PDD, BDSD) and update CLAUDE.md.
Install expo-video, expo-sharing, @expo-google-fonts/inter.

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

app.json

@@ -9,7 +9,8 @@
     "userInterfaceStyle": "automatic",
     "newArchEnabled": true,
     "ios": {
-      "supportsTablet": true
+      "supportsTablet": true,
+      "bundleIdentifier": "com.anonymous.tabatago"
     },
     "android": {
       "adaptiveIcon": {
@@ -38,7 +39,8 @@
             "backgroundColor": "#000000"
           }
         }
-      ]
+      ],
+      "expo-video"
     ],
     "experiments": {
       "typedRoutes": true,