fix: add better error for user binding called ASSETS in pages projects #4573

Job	Run time
Checks	0s
Add PR to project	1s
Checks	1m 10s
Tests (macos-13, ./fixtures/*)	2m 10s
Tests (macos-13, ./packages/*)	1m 36s
Tests (ubuntu-latest, ./fixtures/*)	45s
Tests (ubuntu-latest, ./packages/*)	49s
Tests (ubuntu-latest, ./tools)	41s
Tests (windows-latest, ./fixtures/*)	1m 40s
Tests (windows-latest, ./packages/*)	1m 33s
	10m 25s

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