chore: update release templates empty states in new add strategy modal (#10656)

https://linear.app/unleash/issue/2-3876/update-the-release-templates-section-accordingly

Updates the release templates empty states in the new add strategy modal
to match the new design sketches.

Also fixes a few details in the modal base design.

<img width="989" height="583" alt="image"
src="https://github.com/user-attachments/assets/b3148fe1-eb61-48d5-84cb-3dc4381f7c0c"
/>

<img width="981" height="581" alt="image"
src="https://github.com/user-attachments/assets/54f9a4d7-8cde-4f4b-bc9d-dc7114d7e17f"
/>

frontend/src/component/feature/FeatureStrategy/FeatureStrategyMenu/FeatureStrategyMenuCards/FeatureStrategyMenuCards.tsx

@@ -38,8 +38,8 @@ const StyledContainer = styled(Box)(() => ({
 }));
 
 const StyledScrollableContent = styled(Box)(({ theme }) => ({
-    width: '100%',
-    maxHeight: theme.spacing(62),
+    width: theme.breakpoints.values.md,
+    height: theme.spacing(52),
     overflowY: 'auto',
     padding: theme.spacing(4),
     paddingTop: theme.spacing(1),

frontend/src/component/feature/FeatureStrategy/FeatureStrategyMenu/FeatureStrategyMenuCards/FeatureStrategyMenuCardsReleaseTemplates.tsx

@@ -1,9 +1,9 @@
 import { useReleasePlanTemplates } from 'hooks/api/getters/useReleasePlanTemplates/useReleasePlanTemplates';
 import useUiConfig from 'hooks/api/getters/useUiConfig/useUiConfig';
-import FactCheckOutlinedIcon from '@mui/icons-material/FactCheckOutlined';
+import { ReactComponent as ReleaseTemplateIcon } from 'assets/img/releaseTemplates.svg';
 import { FeatureReleasePlanCard } from '../FeatureReleasePlanCard/FeatureReleasePlanCard.tsx';
 import type { IReleasePlanTemplate } from 'interfaces/releasePlans.ts';
-import { Box, Button, styled, Typography } from '@mui/material';
+import { Box, Button, styled } from '@mui/material';
 import type { StrategyFilterValue } from './FeatureStrategyMenuCards.tsx';
 import type { Dispatch, SetStateAction } from 'react';
 import { Link as RouterLink } from 'react-router-dom';
@@ -14,38 +14,61 @@ import {
 
 const RELEASE_TEMPLATE_DISPLAY_LIMIT = 5;
 
-const StyledIcon = styled('span')(({ theme }) => ({
-    width: theme.spacing(3),
+const StyledIcon = styled('span', {
+    shouldForwardProp: (prop) => prop !== 'solo',
+})<{ solo?: boolean }>(({ theme, solo }) => ({
     '& > svg': {
         fill: theme.palette.primary.main,
-        width: theme.spacing(2.25),
-        height: theme.spacing(2.25),
+        width: theme.spacing(6),
+        height: theme.spacing(6),
+        ...(solo && {
+            width: theme.spacing(10),
+            height: theme.spacing(10),
+        }),
     },
     display: 'flex',
     alignItems: 'center',
 }));
 
-const StyledNoTemplatesContainer = styled(Box)(({ theme }) => ({
-    display: 'flex',
-    flexDirection: 'column',
-    alignItems: 'flex-start',
-    justifyContent: 'flex-start',
-    backgroundColor: theme.palette.neutral.light,
-    borderRadius: theme.shape.borderRadiusMedium,
-    padding: theme.spacing(3),
-    width: 'auto',
-}));
-
-const StyledNoTemplatesTitle = styled(Typography)(({ theme }) => ({
-    fontSize: theme.typography.caption.fontSize,
-    fontWeight: theme.typography.fontWeightBold,
-    marginBottom: theme.spacing(1),
+const StyledNoTemplatesContainer = styled(Box, {
+    shouldForwardProp: (prop) => prop !== 'solo',
+})<{ solo?: boolean }>(({ theme, solo }) => ({
     display: 'flex',
     alignItems: 'center',
+    backgroundColor: theme.palette.neutral.light,
+    borderRadius: theme.shape.borderRadiusMedium,
+    padding: theme.spacing(2),
+    gap: theme.spacing(1),
+    width: 'auto',
+    ...(solo && {
+        backgroundColor: undefined,
+        flexDirection: 'column',
+        maxWidth: theme.spacing(70),
+        margin: 'auto',
+        gap: theme.spacing(2.5),
+    }),
 }));
 
-const StyledNoTemplatesDescription = styled(Typography)(({ theme }) => ({
+const StyledNoTemplatesBody = styled(Box, {
+    shouldForwardProp: (prop) => prop !== 'solo',
+})<{ solo?: boolean }>(({ theme, solo }) => ({
+    display: 'flex',
+    flexDirection: 'column',
+    gap: theme.spacing(0.5),
     fontSize: theme.typography.caption.fontSize,
+    ...(solo && {
+        alignItems: 'center',
+        textAlign: 'center',
+        gap: theme.spacing(2),
+        fontSize: theme.typography.body2.fontSize,
+    }),
+}));
+
+const StyledNoTemplatesTitle = styled('p')(({ theme }) => ({
+    fontWeight: theme.typography.fontWeightBold,
+}));
+
+const StyledNoTemplatesDescription = styled('p')(({ theme }) => ({
     color: theme.palette.text.secondary,
 }));
 
@@ -83,34 +106,46 @@ export const FeatureStrategyMenuCardsReleaseTemplates = ({
         return null;
     }
 
-    const slicedTemplates =
-        filter === 'releaseTemplates'
+    const isFiltered = filter === 'releaseTemplates';
+    const shouldShowHeader = !isFiltered || templates.length > 0;
+
+    const slicedTemplates = isFiltered
         ? templates
         : templates.slice(0, RELEASE_TEMPLATE_DISPLAY_LIMIT);
 
     return (
         <Box>
+            {shouldShowHeader && (
                 <StyledStrategyModalSectionHeader>
-                <Typography color='inherit' variant='body2'>
                     Release templates
-                </Typography>
                 </StyledStrategyModalSectionHeader>
+            )}
             {!templates.length ? (
-                <StyledNoTemplatesContainer>
-                    <StyledNoTemplatesTitle>
-                        <StyledIcon>
-                            <FactCheckOutlinedIcon />
+                <StyledNoTemplatesContainer solo={isFiltered}>
+                    <StyledIcon solo={isFiltered}>
+                        <ReleaseTemplateIcon />
                     </StyledIcon>
-                        Create your own release templates
+                    <StyledNoTemplatesBody solo={isFiltered}>
+                        <StyledNoTemplatesTitle>
+                            You don't have any release templates set up yet
                         </StyledNoTemplatesTitle>
                         <StyledNoTemplatesDescription>
-                        Standardize your rollouts and save time by reusing
-                        predefined strategies. Find release templates in the
-                        side menu under{' '}
+                            Go to{' '}
                             <StyledLink to='/release-templates'>
                                 Configure &gt; Release templates
+                            </StyledLink>{' '}
+                            in the side menu to make your rollouts more
+                            efficient and streamlined. Read more in our{' '}
+                            <StyledLink
+                                to='https://docs.getunleash.io/reference/release-templates'
+                                target='_blank'
+                                rel='noreferrer'
+                            >
+                                documentation
                             </StyledLink>
+                            .
                         </StyledNoTemplatesDescription>
+                    </StyledNoTemplatesBody>
                 </StyledNoTemplatesContainer>
             ) : (
                 <FeatureStrategyMenuCardsSection>

frontend/src/component/feature/FeatureStrategy/FeatureStrategyMenu/FeatureStrategyMenuCards/FeatureStrategyMenuCardsSection.tsx

@@ -1,4 +1,4 @@
-import { Box, styled, Typography } from '@mui/material';
+import { Box, styled } from '@mui/material';
 import type { ReactNode } from 'react';
 
 export const StyledStrategyModalSectionHeader = styled(Box)(({ theme }) => ({
@@ -7,6 +7,7 @@ export const StyledStrategyModalSectionHeader = styled(Box)(({ theme }) => ({
     gap: theme.spacing(0.5),
     marginBottom: theme.spacing(0.5),
     width: '100%',
+    fontSize: theme.typography.body2.fontSize,
 }));
 
 const StyledStrategyModalSectionGrid = styled(Box)(({ theme }) => ({
@@ -28,9 +29,7 @@ export const FeatureStrategyMenuCardsSection = ({
     <Box>
         {title && (
             <StyledStrategyModalSectionHeader>
-                <Typography color='inherit' variant='body2'>
                 {title}
-                </Typography>
             </StyledStrategyModalSectionHeader>
         )}
         <StyledStrategyModalSectionGrid>