Fix Receive by fulfillment setting compatibility

[dt2patel]

Stores with Receive by fulfillment enabled as true currently see the toggle off and receive quantity calculations based on ordered rather than fulfilled quantity. Toggling it on writes Y, which is incompatible with the OMS true check.

This restores the existing true/false contract for RECEIVE_BY_FULFILL: the getter accepts boolean true after loading and the string true immediately after saving, and the toggle saves true/false. Other settings retain their existing Y/N behavior. No backend or production data changes.

Closes #741.

Validation:

• Seven new store regression tests cover existing true/false values, immediate save and reload, missing settings, and unchanged force-scan Y/N behavior.
• The two enabled-setting regression cases fail against unfixed main and pass with the fix.
• vitest run src/store/productStore.settings.spec.ts src/composables/useReceiveFlowState.spec.ts src/views/transferOrderDetailReceiveWorkflow.spec.ts: 13 passed.
• vite build: passed using the isolated worktree and example environment configuration.
• git diff --check: passed.

Read-only Tathya evidence established Gorjana's saved setting is true. Unit tests use API fixtures; an authenticated browser check against Gorjana has not been performed. This PR does not migrate any stores that already have Y/N saved for this setting.

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[ravilodhi]

Handled in this PR - #744

Closing this PR.