design: style Snackbar and Alert with minimalist warm monochrome palette

client/src/app/providers/AppProviders.tsx

@@ -199,6 +199,108 @@ function AppThemeInner({ children }: PropsWithChildren) {
               },
             },
           },
+          MuiAlert: {
+            styleOverrides: {
+              root: {
+                borderRadius: 12,
+                border: '1px solid',
+                boxShadow: 'none',
+                fontWeight: 500,
+                '& .MuiAlert-icon': {
+                  padding: 0,
+                },
+              },
+              standardSuccess: {
+                bgcolor: isDark ? 'rgba(102,187,106,0.08)' : '#EDF3EC',
+                borderColor: isDark ? 'rgba(102,187,106,0.2)' : '#C5DFC2',
+                color: isDark ? '#A5D6A7' : '#346538',
+                '& .MuiAlert-icon': {
+                  color: isDark ? '#A5D6A7' : '#346538',
+                },
+              },
+              standardError: {
+                bgcolor: isDark ? 'rgba(239,83,80,0.08)' : '#FDEBEC',
+                borderColor: isDark ? 'rgba(239,83,80,0.2)' : '#F5C6C7',
+                color: isDark ? '#EF9A9A' : '#9F2F2D',
+                '& .MuiAlert-icon': {
+                  color: isDark ? '#EF9A9A' : '#9F2F2D',
+                },
+              },
+              standardWarning: {
+                bgcolor: isDark ? 'rgba(255,183,77,0.08)' : '#FBF3DB',
+                borderColor: isDark ? 'rgba(255,183,77,0.2)' : '#F0DCA0',
+                color: isDark ? '#FFD54F' : '#956400',
+                '& .MuiAlert-icon': {
+                  color: isDark ? '#FFD54F' : '#956400',
+                },
+              },
+              standardInfo: {
+                bgcolor: isDark ? 'rgba(121,134,203,0.08)' : '#E1F3FE',
+                borderColor: isDark ? 'rgba(121,134,203,0.2)' : '#B8D8F0',
+                color: isDark ? '#9FA8DA' : '#1F6C9F',
+                '& .MuiAlert-icon': {
+                  color: isDark ? '#9FA8DA' : '#1F6C9F',
+                },
+              },
+              outlinedSuccess: {
+                borderColor: isDark ? 'rgba(102,187,106,0.3)' : '#C5DFC2',
+                color: isDark ? '#A5D6A7' : '#346538',
+                '& .MuiAlert-icon': {
+                  color: isDark ? '#A5D6A7' : '#346538',
+                },
+              },
+              outlinedError: {
+                borderColor: isDark ? 'rgba(239,83,80,0.3)' : '#F5C6C7',
+                color: isDark ? '#EF9A9A' : '#9F2F2D',
+                '& .MuiAlert-icon': {
+                  color: isDark ? '#EF9A9A' : '#9F2F2D',
+                },
+              },
+              outlinedWarning: {
+                borderColor: isDark ? 'rgba(255,183,77,0.3)' : '#F0DCA0',
+                color: isDark ? '#FFD54F' : '#956400',
+                '& .MuiAlert-icon': {
+                  color: isDark ? '#FFD54F' : '#956400',
+                },
+              },
+              outlinedInfo: {
+                borderColor: isDark ? 'rgba(121,134,203,0.3)' : '#B8D8F0',
+                color: isDark ? '#9FA8DA' : '#1F6C9F',
+                '& .MuiAlert-icon': {
+                  color: isDark ? '#9FA8DA' : '#1F6C9F',
+                },
+              },
+              filledSuccess: {
+                bgcolor: isDark ? 'rgba(102,187,106,0.15)' : '#346538',
+                color: isDark ? '#E8F5E9' : '#FFFFFF',
+              },
+              filledError: {
+                bgcolor: isDark ? 'rgba(239,83,80,0.15)' : '#9F2F2D',
+                color: isDark ? '#FFEBEE' : '#FFFFFF',
+              },
+              filledWarning: {
+                bgcolor: isDark ? 'rgba(255,183,77,0.15)' : '#956400',
+                color: isDark ? '#FFF8E1' : '#FFFFFF',
+              },
+              filledInfo: {
+                bgcolor: isDark ? 'rgba(121,134,203,0.15)' : '#1F6C9F',
+                color: isDark ? '#E8EAF6' : '#FFFFFF',
+              },
+            },
+          },
+          MuiSnackbarContent: {
+            styleOverrides: {
+              root: {
+                borderRadius: 12,
+                border: '1px solid',
+                borderColor: isDark ? 'rgba(255,255,255,0.1)' : 'rgba(0,0,0,0.06)',
+                bgcolor: isDark ? '#1E1E1E' : '#FFFFFF',
+                boxShadow: '0 2px 12px rgba(0,0,0,0.06)',
+                color: isDark ? '#F2F2F2' : '#1F1B16',
+                fontWeight: 500,
+              },
+            },
+          },
         },
       }),
     [controller.resolvedMode, controller.scheme],

client/src/shared/ui/CartSnackbar.tsx

@@ -25,12 +25,50 @@ export function CartSnackbar() {
       onClose={handleClose}
       anchorOrigin={{ vertical: 'bottom', horizontal: 'center' }}
       autoHideDuration={4000}
+      sx={{
+        '& .MuiSnackbarContent-root': {
+          borderRadius: 12,
+          border: '1px solid',
+          borderColor: 'rgba(0,0,0,0.06)',
+          bgcolor: 'background.paper',
+          boxShadow: '0 4px 20px rgba(0,0,0,0.08)',
+        },
+      }}
     >
       <Alert
         severity="success"
+        variant="standard"
         onClose={handleClose}
+        sx={{
+          bgcolor: 'transparent',
+          border: 'none',
+          boxShadow: 'none',
+          p: 1.5,
+          '& .MuiAlert-message': {
+            fontSize: '0.875rem',
+            fontWeight: 600,
+          },
+          '& .MuiAlert-action': {
+            mr: 0,
+          },
+        }}
         action={
-          <Button color="success" size="small" onClick={handleGoToCart}>
+          <Button
+            size="small"
+            variant="text"
+            onClick={handleGoToCart}
+            sx={{
+              fontWeight: 600,
+              fontSize: '0.8125rem',
+              px: 1.5,
+              py: 0.5,
+              borderRadius: 8,
+              color: 'success.main',
+              '&:hover': {
+                bgcolor: 'action.hover',
+              },
+            }}
+          >
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           </Button>
         }