feat: add dashboard errors tab

[evrendom]

Summary

• activate the redesigned Errors tab on /dashboard
• add a narrow errors data hook plus dashboard error adapters and charts/tables for the new slice
• add the additive analytics.errors.dashboard contract and enrich analytics.errors.trends with error type breakdowns used by the dashboard view
• extend API coverage for the new errors dashboard route and richer trends payload

Test plan

• bun run lint
• bun run --cwd apps/web check-types
• bun run --cwd apps/web test
• bun run --cwd apps/web build
• bun test ./packages/api-routes/src/tests/analytics-schema.test.ts
• bun run verify
  • currently fails in unrelated existing apps/api Drizzle typing code under apps/api/src/handlers/admin/delete-user.ts

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