feat: add template setup wizard, starter walkthrough, and activity roadmap

[mackeh]

Summary

• add a template setup model with required inputs, connection checks, sample input, and runbook metadata
• add template detail endpoint at /api/templates/:templateId and expose setup data from template APIs
• add in-app Template Setup Wizard with preflight validation and readiness gating before create-from-template
• add in-app Starter Walkthrough flow for first-time onboarding
• expand activity catalog into phased pack roadmap (system/core, data table, file, interaction, orchestrator, office, AI, DU, CV, DB, FTP, terminal, crypto)
• add dedicated template quality gate tests and CI step via npm run test:templates
• update README/docs/demos/contributing/changelog and add docs/ACTIVITY_PACK_ROADMAP.md

Validation

• cd apps/server && npm test
• cd apps/server && npm run test:templates
• cd apps/server && npm run build
• cd apps/web && npm test
• cd apps/web && npm run build

Notes

• e2e mock API updated for the new template detail endpoint and activity roadmap fields
• changes are additive and backward-compatible for existing workflow execution