Rebuild Home around a forest header with streak, score and water

Home now opens on a deep green header: greeting, a Today / Weekly toggle,
a seven-day streak with a leaf on every kept day, minutes held with a +
ring, plan thumbnails, the report-card letter as the score, and one bar per
commitment class (weekly view swaps in per-day bars and class rates). The
+ opens an "Add to today" sheet over the blurred day. A water tracker sits
below the header, kept on the device. The nav marks the selected tab as a
filled block and drops the side action button.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KhQh614DMeYoQEH9SoMRUw

frontend/lib/Grounded/mock/MockMemory.dart

@@ -19,6 +19,7 @@ class MockMemory extends InternalMemory {
       setMyDescription(
           MeDescription(id: "mock-user", name: "Alex", token: "mock-token"));
       setUserDetails(UserDetails(pic: "", name: "Alex"));
+      setWaterToday(1250);
       setTodos(<TodoItem>[
         TodoItem(id: "t1", title: "Refill water bottle"),
         TodoItem(id: "t2", title: "Book physio for Thursday"),