feat(experiment): use backend type filter for multivariate features

[Zaimwa9]

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• I have read the Contributing Guide.
• I have added information to docs/ if required so people know about the feature.
• I have filled in the "Changes" section below.
• I have filled in the "How did you test this code" section below.

Changes

Contributes to #7596

• Use backend type=MULTIVARIATE query param instead of client-side filtering in the experiment wizard feature select — fixes pagination issues where multivariate flags on later pages were invisible
• Attach full ProjectFlag object to Select options, removing the .find() lookup that could hit race conditions during search
• Disable react-select client-side filtering since results are already server-filtered
• Add Storybook stories for VariationTable and ContentCard components

How did you test this code?

• Open experiment creation wizard, confirm feature select only shows multivariate flags
• Type in the select — verify server-side search works (debounced)
• Select a feature — verify variation table renders correctly
• Run Storybook and check VariationTable and ContentCard stories render

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Project	Deployment	Actions	Updated (UTC)
flagsmith-frontend-preview	Ready	Preview, Comment	May 28, 2026 3:48pm
flagsmith-frontend-staging	Ready	Preview, Comment	May 28, 2026 3:48pm

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Ignored	Preview	May 28, 2026 3:48pm

[gemini-code-assist]

Code Review

This pull request updates the feature list query to filter by FeatureType on the server side, specifically fetching only multivariate features for the experiment setup step. It also simplifies the selection logic in SetupStep.tsx and adds Storybook stories for ContentCard and VariationTable. Feedback is provided regarding the filterOption prop in react-select, which is currently typed and implemented incorrectly; it should be updated to () => true to cleanly disable client-side filtering.

[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-e2e:pr-7630	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-api:pr-7630	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-api-test:pr-7630	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith:pr-7630	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-7630	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-frontend:pr-7630	Finished ✅	Results ✅

[github-actions]

Playwright Test Results (oss - depot-ubuntu-latest-arm-16)

 1 passed

Details

 1 test across 1 suite
 41.8 seconds
 549ba70
 🔄 Run: #17082 (attempt 1)

Playwright Test Results (oss - depot-ubuntu-latest-16)

 1 passed

Details

 1 test across 1 suite
 39.3 seconds
 549ba70
 🔄 Run: #17082 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-16)

 3 passed

Details

 3 tests across 3 suites
 36.5 seconds
 549ba70
 🔄 Run: #17082 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-arm-16)

 1 passed

Details

 1 test across 1 suite
 1 minute, 4 seconds
 549ba70
 🔄 Run: #17082 (attempt 1)

Playwright Test Results (oss - depot-ubuntu-latest-arm-16)

 1 passed

Details

 1 test across 1 suite
 42.8 seconds
 07cbfeb
 🔄 Run: #17084 (attempt 1)

Playwright Test Results (oss - depot-ubuntu-latest-16)

 1 passed

Details

 1 test across 1 suite
 38.9 seconds
 07cbfeb
 🔄 Run: #17084 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-16)

 3 passed

Details

 3 tests across 3 suites
 31.9 seconds
 07cbfeb
 🔄 Run: #17084 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-arm-16)

 2 passed

Details

 2 tests across 2 suites
 39.9 seconds
 07cbfeb
 🔄 Run: #17084 (attempt 1)

Playwright Test Results (oss - depot-ubuntu-latest-arm-16)

 1 passed

Details

 1 test across 1 suite
 41.5 seconds
 0c220df
 🔄 Run: #17087 (attempt 1)

Playwright Test Results (oss - depot-ubuntu-latest-16)

 1 passed

Details

 1 test across 1 suite
 39.1 seconds
 0c220df
 🔄 Run: #17087 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-arm-16)

 3 passed

Details

 3 tests across 3 suites
 35.1 seconds
 0c220df
 🔄 Run: #17087 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-16)

 3 passed

Details

 3 tests across 3 suites
 52.6 seconds
 0c220df
 🔄 Run: #17087 (attempt 1)

[github-actions]

Visual Regression

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[talissoncosta]

Thanks for handling that! Looks great!