feat: HA/Google edit, full-page event detail, KW+zigzag divider, HSV picker, splash

- Home Assistant & Google events now editable/deletable (server PUT/DELETE
  endpoints wired; saveEvent had no HA/Google update branch -> created dupes)
- Event detail is now a full screen (Scaffold) instead of a bottom sheet:
  long notes scroll, action buttons no longer hidden behind the system nav bar;
  distinct calendar vs notes icons
- Month view: calendar-week number on Mondays, month-boundary divider with
  zigzag step (month_divider_color), month label in month_label_color,
  text/line contrast applied
- Compact top bar with smaller title; prev/next chevrons present in month view
  and scroll one month at a time
- Real HSV colour picker (SV field + hue slider + hex) for primary, accent,
  today, month-divider and month-label colours
- Black status/navigation bars; portrait-locked; crisp custom splash with app
  name, high-res icon and © Scarriffle

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/res/values/themes.xml

@@ -1,10 +1,11 @@
 <resources>
-    <color name="splash_bg">#0B1220</color>
+    <color name="splash_bg">#000000</color>
 
     <style name="Theme.Calendarr" parent="Theme.Material3.DayNight.NoActionBar">
-        <!-- Dark window background avoids a white flash before Compose draws. -->
+        <!-- Black window/system bars (matches the app background). -->
         <item name="android:windowBackground">@color/splash_bg</item>
-        <item name="android:statusBarColor">@color/splash_bg</item>
-        <item name="android:navigationBarColor">@color/splash_bg</item>
+        <item name="android:statusBarColor">@android:color/black</item>
+        <item name="android:navigationBarColor">@android:color/black</item>
+        <item name="android:windowLightStatusBar">false</item>
     </style>
 </resources>