feat: rebuild desktop UI to match Figma + website, hero slider improvements

- Desktop sidebar (262px, blue gradient, white pill nav), topbar (search + bell + avatar), responsive shell rewritten
- Desktop homepage: immersive hero with Ken Burns animation, pill category chips, date badge cards matching mvnew.eventifyplus.com/home
- Desktop calendar: 60/40 two-column layout with white background
- Desktop profile: full-width banner + 3-column event grids
- Desktop learn more: hero image + about/venue columns + gallery strip
- Desktop settings/contribute: polished to match design system
- Mobile hero slider: RepaintBoundary, animated dots with 44px tap targets, 5s auto-scroll, 8s post-swipe delay, shimmer loading, dynamic event type badge, human-readable dates
- Guest access: requiresAuth false on read endpoints
- Location fix: show place names instead of lat/lng coordinates
- Version 1.6.1+17

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

lib/widgets/landscape_shell.dart

@@ -0,0 +1,67 @@
+// lib/widgets/landscape_shell.dart
+//
+// Reusable two-panel landscape scaffold for all desktop/wide screens.
+// Left panel uses the brand dark-blue gradient; right panel is the content area.
+//
+// Usage:
+//   LandscapeShell(
+//     leftPanel: MyLeftContent(),
+//     rightPanel: MyRightContent(),
+//   )
+
+import 'package:flutter/material.dart';
+import '../core/app_decoration.dart';
+
+class LandscapeShell extends StatelessWidget {
+  final Widget leftPanel;
+  final Widget rightPanel;
+
+  /// Flex weight for left panel (default 2 → ~40% of width)
+  final int leftFlex;
+
+  /// Flex weight for right panel (default 3 → ~60% of width)
+  final int rightFlex;
+
+  /// Optional background color for right panel (defaults to scaffold background)
+  final Color? rightBackground;
+
+  const LandscapeShell({
+    Key? key,
+    required this.leftPanel,
+    required this.rightPanel,
+    this.leftFlex = 2,
+    this.rightFlex = 3,
+    this.rightBackground,
+  }) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    final bg = rightBackground ?? Theme.of(context).scaffoldBackgroundColor;
+    return Row(
+      crossAxisAlignment: CrossAxisAlignment.stretch,
+      children: [
+        // ── Left panel — dark blue gradient ──────────────────────────────
+        Flexible(
+          flex: leftFlex,
+          child: RepaintBoundary(
+            child: Container(
+              decoration: AppDecoration.blueGradient,
+              child: leftPanel,
+            ),
+          ),
+        ),
+
+        // ── Right panel — content area ────────────────────────────────────
+        Flexible(
+          flex: rightFlex,
+          child: RepaintBoundary(
+            child: ColoredBox(
+              color: bg,
+              child: rightPanel,
+            ),
+          ),
+        ),
+      ],
+    );
+  }
+}