chore: Add GitHub hardening files (CODEOWNERS, SECURITY.md, dependabot)

Part of Phase 4 - GitHub structure hardening for Orcest AI ecosystem.

Co-Authored-By: Danial Piterson <danial.samiei@gmail.com>

.github/CODEOWNERS

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+# Default code owners for all files
+* @danialsamiei
+

.github/dependabot.yml

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+version: 2
+updates:
+  - package-ecosystem: "npm"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 5
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 5

SECURITY.md

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+# Security Policy
+
+## Supported Versions
+
+| Version | Supported |
+|---------|-----------|
+| Latest  | Yes       |
+
+## Reporting a Vulnerability
+
+If you discover a security vulnerability, please report it responsibly:
+
+1. **Do NOT** open a public GitHub issue
+2. Use [GitHub Security Advisories](https://github.com/orcest-ai/Orcide/security/advisories/new) to report privately
+3. Or email: support@orcest.ai
+
+We will acknowledge receipt within 48 hours and provide a timeline for resolution.
+
+## Security Best Practices
+
+- All secrets must be stored in environment variables, never in code
+- All services require SSO authentication via login.orcest.ai
+- API keys must be rotated regularly
+- All traffic must use HTTPS/TLS
+
+Part of the [Orcest AI](https://orcest.ai) ecosystem.
+