Add observability and security-hardening proposals, gitignore settings.local

Two new OpenSpec changes:
- observability (30 tasks): health endpoints, Prometheus, Grafana+Loki,
  structured logging, dashboards, alerting
- security-hardening (24 tasks): Caddy headers, scanner blocking,
  gitleaks, pnpm audit, dependabot, non-root Docker, fail2ban

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

openspec/changes/security-hardening/tasks.md

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+## 1. Caddy Security Headers
+
+- [ ] 1.1 Add security headers block to Caddyfile: HSTS, X-Content-Type-Options, X-Frame-Options, Referrer-Policy, Permissions-Policy
+- [ ] 1.2 Add Content-Security-Policy header (permissive initial policy allowing React Router inline scripts, OSM tiles, Sentry, WebSocket)
+- [ ] 1.3 Test headers with securityheaders.com or curl after deploy
+
+## 2. Scanner Blocking
+
+- [ ] 2.1 Add Caddy path matcher for common scanner targets (.env*, .git*, wp-*, admin*, config.*, backup*)
+- [ ] 2.2 Return 403 for matched paths before reverse_proxy
+- [ ] 2.3 Verify scanner paths return 403, normal paths still work
+
+## 3. CI Secret Scanning
+
+- [ ] 3.1 Add gitleaks/gitleaks-action@v2 step to CI workflow
+- [ ] 3.2 Create .gitleaks.toml with allowlist for Sentry DSNs (public values)
+- [ ] 3.3 Verify gitleaks passes on current codebase
+
+## 4. Dependency Auditing
+
+- [ ] 4.1 Add `pnpm audit --audit-level=high` step to CI workflow
+- [ ] 4.2 Create .github/dependabot.yml for weekly pnpm dependency updates
+- [ ] 4.3 Verify pnpm audit passes on current codebase
+
+## 5. Docker Hardening
+
+- [ ] 5.1 Add non-root user to Journal Dockerfile runtime stage
+- [ ] 5.2 Add non-root user to Planner Dockerfile runtime stage
+- [ ] 5.3 Add non-root user to BRouter Dockerfile
+- [ ] 5.4 Test containers start and serve correctly as non-root
+
+## 6. Server Hardening
+
+- [ ] 6.1 Install and configure fail2ban on Hetzner server (SSH protection)
+- [ ] 6.2 Configure UFW firewall (allow 22, 80, 443 only)
+- [ ] 6.3 Document server hardening steps in deployment docs
+
+## 7. Documentation
+
+- [ ] 7.1 Create SECURITY.md with vulnerability disclosure policy and security contact
+- [ ] 7.2 Update privacy manifest with security practices documented
+
+## 8. Verify
+
+- [ ] 8.1 Run securityheaders.com scan on trails.cool and planner.trails.cool
+- [ ] 8.2 Verify scanner paths return 403 in production
+- [ ] 8.3 Verify CI passes with all new scanning steps
+- [ ] 8.4 Verify Docker containers run as non-root