refactor(mirrors): drop denormalized ProductMirror.storage_type

[alukach]

Stacked on #453 (base is fix/gcs-provider-alignment) — review/merge that first; GitHub will retarget this to main once it lands.

Why

Nothing branched on storage_type: the data proxy keys off the connection's details.provider, and the only source.coop consumer was a display label. It was a denormalized copy of the provider, bridged by a cast. This removes the field entirely — dissolving the "two vocabularies" problem rather than just aligning it.

Changes

• Drop storage_type from ProductMirrorSchema; stop writing it in createProduct / addProductMirror (removes both provider→storage_type casts and the invariant test they needed).
• Mirror "Type" label now reads the provider from connectionInfo (sourced from the connection's details.provider on the edit page).
• No migration: ProductMirrorSchema is a plain z.object, so existing records still carrying storage_type parse fine (unknown key stripped).

Verification

tsc clean · jest affected suites 116/116 · lint clean on changed files.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
source-cooperative	Ready	Preview, Comment	Jul 22, 2026 5:55pm

[claude]

Claude finished @alukach's task in 1m 29s —— View job

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Reviewing PR #454

• Gather context (diff, changed files)
• Review diff for correctness/security/best-practice issues
• Post findings

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✅ No blocking issues — safe to merge.

• The storage_type removal is fully self-consistent: every producer (createProduct, addProductMirror) and consumer (ProductMirrorsManager, tests) was updated together, and no other reference to ProductMirror.storage_type remains in src/ (verified via repo-wide grep).
• Since ProductMirrorSchema is a plain z.object (not .strict()), existing DynamoDB rows that still carry storage_type will continue to parse fine — the unknown key is silently stripped, matching the PR's stated no-migration claim.
• src/app/(app)/edit/.../data-connections/page.tsx:59 correctly sources provider from the connection's details.provider and threads it through connectionInfo into ProductMirrorsManager.tsx:238.

One minor (non-blocking) behavior note for awareness, not a regression introduced by sloppy code:

• ProductMirrorsManager.tsx:236-240 — the "Type" field now renders connectionInfo[mirror.connection_id]?.provider, which is undefined (blank) for a mirror whose connection has since been deleted, whereas the old mirror.storage_type would still show the last-known type for such orphaned mirrors. This mirrors the pre-existing behavior of the "Bucket" field (already connection-dependent), so it's consistent with the rest of the component rather than a new gap — flagging only in case a blank "Type" for orphaned mirrors is undesired.

[alukach]

Re-split into #455 (value alignment) + #456 (storage_type removal, now also owns the map deletion).