[APPS] Move inlineDynamicImports to shared backend build config

[sdkennedy2]

Motivation

Both the production build (buildBackendFunctions) and dev server build (bundleFunction) were independently setting inlineDynamicImports: true in their rollup output config. This duplication meant the shared base config didn't fully capture the contract that all backend function builds produce self-contained JS files.

Changes

Moved inlineDynamicImports: true into getBaseBackendBuildConfig so the shared config is the single source of truth for backend build behavior. Removed the redundant per-caller overrides and cleaned up stale comments that referenced the now-centralized setting.

Also inlined the virtualEntries variable in the production build loop — since we build one function at a time, there's no need for an intermediate variable holding a single-entry map.

QA Instructions

This is a pure refactor with no behavior change. The same inlineDynamicImports: true setting is applied in the same place — just from the shared config instead of each caller.

• Existing unit tests for backend function building should pass
• E2E tests for apps with backend functions should produce identical output

Blast Radius

• Only affects the apps plugin's backend function build path (Vite only)
• No customer-facing API or config changes
• Gated behind the apps plugin feature flag

Documentation

• How to reliably make frontend production changes
• PR Description Guidelines
• Deploy steps

[sdkennedy2]

• [APPS] Move inlineDynamicImports to shared backend build config #317 👈 (View in Graphite)
• [APPS] Add vite dev server middleware for backend functions #291 : 1 other dependent PR (#306 )
• [APPS] Use separate vite.build() for backend functions, drop Rollup backend support #292
• master

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[datadog-official]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

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