Improve manual coding performance

[jurei733]

Summary

Refs #813

This PR improves the perceived and measured performance of the manual coding administration flows, especially for testergebnisse, Kodierübersicht, and manuelle Kodierung with auto-refresh enabled.

Changes include:

• response-analysis summary/page/chunk caching to avoid repeatedly serving large cached payloads
• stale-run and source-revision guards for background analysis jobs
• in-flight dedupe and stale-cache protection for manual coding availability data
• faster backend query filters for unit/variable pairs and applied-results counts
• UI race guards so stale auto-refresh responses no longer overwrite the active tab/workspace state
• split transient and priority error overlays so ordinary HTTP errors do not cover navigation, dialogs, or export progress
• Cypress and repro scripts for slow-network, rapid-tab, and large-workspace performance checks

Root Cause

The slow feeling was not mainly caused by Angular rendering. The main sources were backend-side duplicate work and large cached response-analysis payloads being serialized and returned during cache hits. Rapid tab changes and auto-refresh could also start overlapping requests; old responses then risked updating current UI state. For stale paginator states, response-analysis could miss chunk caches and fall back toward heavier paths even though the summary was already available.

Validation

• npx nx test backend --testFile=apps/backend/src/app/database/services/coding/coding-analysis.service.spec.ts --runInBand --skip-nx-cache
• npx nx test backend --testFile=apps/backend/src/app/database/services/coding/coding-job.service.spec.ts --runInBand --skip-nx-cache
• npx nx test backend --testFile=apps/backend/src/app/database/services/coding/coding-validation.service.spec.ts --runInBand --skip-nx-cache
• npx nx test frontend --testFile=apps/frontend/src/app/shared/components/error-message-display/error-message-display.component.spec.ts --runInBand --skip-nx-cache
• npx nx lint backend --skip-nx-cache
• npx nx lint frontend --skip-nx-cache
• Cypress UI smoke against http://localhost:4201, workspace 54, slow-4g profile, manual login: 4/4 passing

Notes

The issue is intentionally only referenced and not closed by this PR description. Local disk space was tight during the largest-scale repro work, so further tests beyond 5000 active test persons should be run on a machine with more free space.