chore(lint): manual cleanup batch 4 — noNonNullAssertion + small fixes
- noNonNullAssertion (42 → 0): replaced ! assertions with explicit null guards across auth.module, storage.service, pl24-auth, categories.service, catalog.service, parts.service, emex.browser, emex.service, parts-catalogs-auth, pl24-ford-legacy, email.service, database.provider, jobs/processors, psa-variant-selector, vehicles/$id/categories, catalog/$brandName
- buildTree: skip orphaned items instead of asserting map.get
- emex.browser.acquirePage: explicit context check before newPage
- pcat-auth.getIstanbulTime: graceful UTC fallback if Intl parts missing
- email.send: gate on both postalApiUrl + postalApiKey for type narrowing
- categories.service: PSA root-fallback now early-returns when category.vehicleId missing (catalog-only categories don't have a sibling root)
- pl24-ford-legacy: createHash from "node:crypto", URL building uses single template literals, useDefaultParameterLast — required modelYear/engine/gearbox params (callers already supply them)
- pcat-auth: h.origin / h.referer literal-key access
- index.tsx: <button type="button"> on mobile menu toggle
- parts-panel + admin/users: keyboard handler for clickable rows (Enter/Space)
- ford-legacy: useOptionalChain on item.name?.toUpperCase()
Lint count: 155 → 114. Remaining: 121 noExplicitAny + 3 small.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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