deps: upgrade express middleware and clean outdated dependencies

[Gabbydunkk]

Summary

Upgrades the Express middleware stack and cleans outdated/unused dependencies:

• express ^4.18.2 → ^4.22.2 — latest 4.x line, pulling in the security fixes shipped in 4.19–4.22. A jump to Express 5 is currently blocked by apollo-server-express@3.13's hard peer dependency on express@^4.17.1 (verified: npm install fails with ERESOLVE), and migrating GraphQL to @apollo/server is a separate refactor well beyond this dependency pass.
• connect-redis ^7.1.1 → ^10.0.0 — current line, whose peers (redis >=5, express-session >=1) match what the repo already uses. Updated src/config/redis.ts to the v10 named export (RedisStore) and the two jest mocks that shape it.
• Removed dead dependencies:
  • spdy — the app serves over Node's native http2; only stale test mocks referenced it.
  • pino-loki — unused anywhere.
• Removed the now-unneeded spdy mocks from paymentLink and multisigCallbacks tests.

Verification

• npm install resolves cleanly (no peer conflicts)
• npm run type-check — clean
• npm run build — clean
• npm run lint — 0 errors
• npx prettier --check on all touched files — clean
• Affected test suites behave identically to main (the remaining failures in paymentLink/multisigCallbacks/kycUpload are pre-existing fallout from the recent BullMQ migration — they fail on a clean checkout of main too and are unrelated to this change; the repo's CI test step runs with continue-on-error: true).
• Runtime smoke: RedisStore from connect-redis v10 constructs correctly with the repo's redis v5 client and prefix option.

Closes #1849

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