feat(learning): add flagship roadmap "Deploy a resilient three-tier app" (en/fr)

[OthmaneZ05]

Summary of Changes

Adds the first full-length guided roadmap to the catalog: “Deploy a resilient three-tier app” (roadmaps/resilient-three-tier.json, English reference) and its French translation (roadmaps/resilient-three-tier.fr.json, same roadmap id and step ids so progression carries across languages).

Over 10 steps (~40 min, intermediate), the learner builds and operates a classic three-tier architecture against real containers: a web server backed by a seeded PostgreSQL, a hand-built second replica, an nginx load balancer as single entry point, a least-privilege lockdown of the database (with a deliberate validate-first failure to read), a chaos drill (stop a server while validating through the LB), and an auto-scaling group deployed from a golden image whose clones boot already serving. It exercises 7 of the 9 validator types (container_running, table_exists, edge_exists, http_get_contains, lb_upstreams, port_denied, asg_replicas). Every step ships 2–3 graded hints plus a literal copy-paste solution.

Content only — no engine, schema, or frontend changes.

Types of Changes

• New feature / node type addition
• Bug fix (non-breaking change resolving an issue)
• Refactoring / structural cleanup
• Documentation update

Verification & Testing

Automated Checks

• Run npm run lint successfully with no errors
• Run npm run build successfully with no compilation errors
• Run npm test successfully (all tests pass)

Manual Verification

• npm run roadmap:validate passes on both files; both appear in the player catalog with language, difficulty, step-count and duration badges.
• Played end to end against real Docker: every step observed failing in its naive state, then passing after the instructed action (validators exercised through POST /api/learning/validate with the exact network-config mutations the canvas UI produces).
• Real-traffic counter-checks: after the lockdown step, a TCP attempt from the load balancer to db:5432 is actually refused while the store keeps serving; during the chaos drill nginx fails over to the surviving server; ASG clones serve on boot from the committed golden image.
• Player UI checked with a headless browser: localhost link appears on the expected steps, hint ladder and two-click solution reveal work, backend kill & restart mid-roadmap resumes on the right step with checkmarks restored, and switching EN→FR mid-roadmap keeps the progression.

Checklist

• My code follows the repository's code style and lint standards
• I have updated the documentation or instructions if necessary
• All unit and integration tests are passing