Release v0.2.0

Highlights:
- Element Web optional deployment on Stackit (nginx routing, CORS, TLS precondition)
- Certbot-managed TLS (HTTP-01) replaces ACME DNS-01 on Stackit VM
- Stackit Logs integration (nebu.service → Stackit Observability)
- Dedicated Stackit network resources (network.tf, alb.tf, dns.tf, database.tf, logs.tf)
- PII encryption at rest variable (pii_encryption_key, 64-char hex)
- SSO fix: login tokens inserted before URL fragment — Element Web / Cinny hash-router compatibility
- m.login.token advertised in login flow (Element Web 1.12+ SSO fix)
- Gateway migration squash: 49 migrations → single seed 000001_init.up.sql (PostgresFlex compat)
- Element Web nginx routing security fix (/api/v1/ proxy block + WebSocket headers)
- E2E bootstrap test fixes (PROJECT_ROOT resolution, DEX_ISSUER_URL import)
- WCAG AA Admin UI contrast fixes (primary-content + error-content tokens)
- Fix Docker registry login in CI release jobs