Implement Phase 10: e-ink polish and finalize project docs

- High-contrast theme with expanded color palette for e-ink readability
- Updated source trees in DESIGN.md
- Updated PROJECT_PLAN.md and PROGRESS.md — all phases complete
  (only on-device performance profiling remains)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/src/main/kotlin/net/metacircular/engpad/ui/theme/Theme.kt

@@ -5,13 +5,25 @@ import androidx.compose.material3.lightColorScheme
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.graphics.Color
 
+/**
+ * High-contrast light theme optimized for e-ink displays.
+ * Black on white, no gradients, no subtle color differences.
+ */
 private val LightColorScheme = lightColorScheme(
     primary = Color.Black,
     onPrimary = Color.White,
+    primaryContainer = Color(0xFFE0E0E0),
+    onPrimaryContainer = Color.Black,
+    secondary = Color.DarkGray,
+    onSecondary = Color.White,
     surface = Color.White,
     onSurface = Color.Black,
+    surfaceVariant = Color(0xFFF0F0F0),
+    onSurfaceVariant = Color.Black,
     background = Color.White,
     onBackground = Color.Black,
+    outline = Color.Black,
+    outlineVariant = Color.Gray,
 )
 
 @Composable