refactor: dedupe event-payload & request-guard helpers; fail lint on warnings

[willy-de7]

Resolves three small, independently-tracked tech-debt items in one pass. Each is a mechanical change with no runtime behaviour change (except CI strictness in #133).

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closes #133 — pnpm lint never fails on ESLint warnings

"lint": "eslint ." exits 0 for a run that produces only warnings. eslint.config.js has exactly one warn-severity rule (no-console), so a reintroduced console.log in src/ would pass both pnpm lint and CI's lint-and-typecheck job silently.

• package.json → "lint": "eslint . --max-warnings=0", matching the all-or-nothing enforcement of format:check / typecheck / test.

Acceptance

• pnpm lint now exits non-zero on any warning.

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closes #131 — blockchain-event payload parsers copy-pasted across ~7 files

parseAddress was defined verbatim in the application-layer event handlers of deliveries, disputes, escrow, fleet, fraud-detection, notifications, reputation (7 copies). A parallel BigInt-id parser was defined independently in deliveries (parseDeliveryId), escrow (parseDeliveryId), fleet (parseFleetId) and disputes (parseBareDeliveryId).

• New src/shared/events/parse.ts exporting parseAddress and a single generically-named parseBigIntId, re-exported from the existing src/shared/events barrel (already an allowed dependency for the application layer per eslint.config.js). Lives next to BlockchainEventEnvelope because this is event-payload-shape parsing, not module business logic.
• All 7 local parseAddress definitions replaced with the shared import.
• parseDeliveryId / parseFleetId / parseBareDeliveryId call sites now use parseBigIntId; the local definitions are removed.
• disputes keeps parseTupleWrappedDeliveryId as a thin, contract-specific wrapper — it now JSON-unwraps and delegates to parseBigIntId.
• notifications keeps parseId (its read model keys by the decimal string form) as a two-line wrapper over parseBigIntId.
• escrow's parseAmount is left local (amounts, not ids — out of scope).

Acceptance

• parseAddress defined in exactly one place.
• Generic BigInt-parsing logic defined in exactly one place; module-specific wrapping (disputes tuple-unwrap, notifications string form) kept local.

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closes #132 — requireUser / requireUserId request-guard copy-pasted across 4 route files

admin, disputes, notifications and users each defined their own near-identical helper (same "unreachable in practice" comment) to narrow request.user after an authenticate preHandler.

• Added requireUser(request): { id: string; role: UserRole } to src/shared/http/plugins/auth-guard.ts — next to authenticate / requireRole, and to the request.user type augmentation it already declares — and re-exported it from src/shared/http/index.js.
• Replaced the four local definitions with the shared import. requireUserId(request) call sites become requireUser(request).id.
• Dropped the now-unused UnauthorizedError (and, in disputes, UserRole) imports from the four route files.

Acceptance

• Helper defined in exactly one place, exported alongside authenticate / requireRole.

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Verification

Pure extraction / mechanical change — no behaviour change. Verified locally that this branch adds zero new pnpm lint, pnpm typecheck, or vitest failures relative to main (the local dev environment has some pre-existing dependency-resolution drift; the diff introduces none of it, and touches no failing file).

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