Add Trash/Shares/Recent tabs, file sharing, Details sheet, and rebrand to Noo

Major additions since the initial rebuild:
- New tabs: Trash, Shares, Recent, configurable tab visibility/order/default
- Nextcloud sharing: search users/teams, internal link, email shares,
  public links, "others with access" - in its own Share bottom sheet
- Details bottom sheet (Info/Versions/Activity) with a persistent peek
  panel in the media viewer, reachable from selection, swipe, and the
  media viewer
- Files/Photos: tap-and-hold multi-select with a sticky selection toolbar,
  swipe actions (favorite/delete/share), sticky sort/filter controls,
  list/grid views, breadcrumb chips, whole-account Photos view
- Media viewer: pinch/double-tap zoom on images, predictive-back support,
  fixed PDF zoom-out floor
- Settings: Material You theming incl. AMOLED black, configurable bottom
  bar tabs, swipe actions, media seek bar style, and folder-listing cache
  policy (never/periodic/manual) to cut down on refetching
- Login flow moved to an in-app Chrome Custom Tab with retry-tolerant
  polling
- Replaced ad hoc widgets with native Material 3 equivalents (toggle
  IconButtons, SliverAppBar selection toolbar, SearchBar, drag handles)
- Rebrand: app renamed to Noo throughout, package id -> dev.ayushya.noo,
  new adaptive launcher icon

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lib/widgets/selectable_thumbnail.dart

@@ -0,0 +1,53 @@
+import 'package:flutter/material.dart';
+
+/// Wraps a thumbnail so it can show the multi-select checkmark state:
+/// dimmed with a checkmark overlaid once selected, matching the Google
+/// Photos-style long-press-to-select pattern. Shared by the Files and
+/// Photos tabs.
+class SelectableThumbnail extends StatelessWidget {
+  final bool isSelected;
+  final Widget child;
+
+  /// Fixed width/height for a small square thumbnail (Files list/grid
+  /// tiles). Leave null to fill whatever space the parent already gives it
+  /// instead (e.g. a Photos grid cell, whose size comes from the grid
+  /// layout rather than a fixed constant).
+  final double? size;
+  final double checkmarkSize;
+
+  const SelectableThumbnail({
+    super.key,
+    required this.isSelected,
+    required this.child,
+    this.size,
+    this.checkmarkSize = 28,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    final stack = Stack(
+      fit: StackFit.expand,
+      children: [
+        Positioned.fill(
+          child: AnimatedOpacity(
+            opacity: isSelected ? 0.35 : 1,
+            duration: const Duration(milliseconds: 150),
+            child: child,
+          ),
+        ),
+        if (isSelected)
+          Center(
+            child: Icon(
+              Icons.check_circle_rounded,
+              color: colorScheme.primary,
+              size: checkmarkSize,
+            ),
+          ),
+      ],
+    );
+
+    if (size == null) return stack;
+    return SizedBox(width: size, height: size, child: stack);
+  }
+}