Security hardening: headers, scanning, Docker, firewall

- Caddy: HSTS, CSP, X-Frame-Options, nosniff, Referrer-Policy,
  Permissions-Policy on all responses
- Caddy: Block scanner paths (.env, .git, wp-config, etc.) with 403
- CI: Gitleaks secret scanning + pnpm audit for vulnerabilities
- Dependabot: Weekly npm + GitHub Actions + monthly Docker updates
- Docker: Non-root user in journal, planner, and brouter containers
- Server: UFW firewall (22/80/443 only) + fail2ban (8 IPs already banned)
- SECURITY.md: Vulnerability disclosure policy
- Privacy page: Security practices section added

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

.github/dependabot.yml

@@ -0,0 +1,30 @@
+version: 2
+updates:
+  - package-ecosystem: "npm"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    groups:
+      production:
+        update-types:
+          - "minor"
+          - "patch"
+      development:
+        dependency-type: "development"
+    open-pull-requests-limit: 10
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 5
+
+  - package-ecosystem: "docker"
+    directory: "/apps/journal"
+    schedule:
+      interval: "monthly"
+
+  - package-ecosystem: "docker"
+    directory: "/apps/planner"
+    schedule:
+      interval: "monthly"