fix(discover): 封面完整显示并移除图上标题

lib/pages/discover/widgets/home_drama_grid.dart

@@ -119,19 +119,12 @@ class _HomeDramaCard extends StatelessWidget {
               child: Stack(
                 fit: StackFit.expand,
                 children: [
-                  RemoteImage(
-                    drama.posterUrl,
-                    fit: BoxFit.cover,
-                    showFallbackIcon: true,
-                  ),
-                  const DecoratedBox(
-                    decoration: BoxDecoration(
-                      gradient: LinearGradient(
-                        begin: Alignment.topCenter,
-                        end: Alignment.bottomCenter,
-                        colors: [Color(0x0D000000), Color(0xCC000000)],
-                        stops: [0.45, 1],
-                      ),
+                  ColoredBox(
+                    color: AppColors.card,
+                    child: RemoteImage(
+                      drama.posterUrl,
+                      fit: BoxFit.contain,
+                      showFallbackIcon: true,
                     ),
                   ),
                   if (free)
@@ -157,22 +150,6 @@ class _HomeDramaCard extends StatelessWidget {
                         ),
                       ),
                     ),
-                  Positioned(
-                    left: 6,
-                    right: 6,
-                    bottom: 6,
-                    child: Text(
-                      drama.title,
-                      maxLines: 1,
-                      overflow: TextOverflow.ellipsis,
-                      style: const TextStyle(
-                        color: AppColors.onPrimary,
-                        fontSize: 9,
-                        fontWeight: FontWeight.w800,
-                        shadows: [Shadow(blurRadius: 6, color: Colors.black)],
-                      ),
-                    ),
-                  ),
                 ],
               ),
             ),