feat: Add DevSecOps tools, Woodpecker proxy, Vault persistent storage, pitch-deck annex slides

- Install Gitleaks, Trivy, Grype, Syft, Semgrep, Bandit in backend-core Dockerfile
- Add Woodpecker SQLite proxy API (fallback without API token)
- Mount woodpecker_data volume read-only to backend-core
- Add backend proxy fallback in admin-core Woodpecker route
- Add Vault file-based persistent storage (config.hcl, init-vault.sh)
- Auto-init, unseal and root-token persistence for Vault
- Add 6 pitch-deck annex slides (Assumptions, Architecture, GTM, Regulatory, Engineering, AI Pipeline)
- Dynamic margin/amortization KPIs in BusinessModelSlide
- Market sources modal with citations in MarketSlide
- Redesign nginx landing page to 3-column layout (Lehrer/Compliance/Core)
- Extend MkDocs nav with Services and SDK documentation sections
- Add SDK Protection architecture doc

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

vault/config.hcl

@@ -0,0 +1,12 @@
+storage "file" {
+  path = "/vault/data"
+}
+
+listener "tcp" {
+  address     = "0.0.0.0:8200"
+  tls_disable = 1
+}
+
+ui = true
+api_addr = "http://0.0.0.0:8200"
+disable_mlock = true