chore: replace Dependabot references with Renovate

- SECURITY.md: update to mention Renovate instead of Dependabot
- README.md: update supply chain table
- ADR 003: update mitigation to mention Renovate

Closes PRI-389. Parent PRI-387.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

README.md

@@ -151,7 +151,7 @@ Plaintext values never leave your browser.
 | Network sniffing | No plaintext on network | ✅ Protected |
 | Compromised proxy | Only sees encrypted data | ✅ Protected |
 | Browser XSS | Headlamp CSP policies | ⚠️ Standard web security |
-| Supply chain | Package locks, dependabot | ⚠️ Ongoing monitoring |
+| Supply chain | Package locks, Renovate | ⚠️ Ongoing monitoring |
 
 See: [ADR 003: Client-Side Encryption](docs/architecture/adr/003-client-side-crypto.md)
 

SECURITY.md

@@ -70,7 +70,7 @@ Key dependencies with security implications:
 - **node-forge**: Used for client-side encryption of secret values with the cluster's sealing certificate. Keep this dependency up to date.
 - **@kinvolk/headlamp-plugin**: Peer dependency providing the Kubernetes API proxy. Update by upgrading your Headlamp installation.
 
-The project uses `npm audit` and Dependabot to monitor for known vulnerabilities.
+The project uses `npm audit` and Renovate to monitor for known vulnerabilities.
 
 ## Contact
 

docs/architecture/adr/003-client-side-crypto.md

@@ -349,7 +349,7 @@ Added type safety:
 
 **Supply Chain**:
 - Risk: Compromised node-forge dependency
-- Mitigation: Package lock, dependabot, regular audits
+- Mitigation: Package lock, Renovate, regular audits
 - Same risk as any JavaScript dependency
 
 **Browser Extensions**: