feat(03-03): add OpenRouter, LiteLLM, Cloudflare, Vercel, Portkey, Helicone gateways

- sk-or-v1- and sk-helicone- high-confidence prefix regex
- LiteLLM low-confidence sk- pattern with master key keyword
- Cloudflare, Vercel, Portkey keyword-anchored detection

providers/litellm.yaml

@@ -0,0 +1,20 @@
+format_version: 1
+name: litellm
+display_name: LiteLLM Proxy
+tier: 5
+last_verified: "2026-04-05"
+keywords:
+  - "litellm"
+  - "LITELLM_API_KEY"
+  - "LITELLM_MASTER_KEY"
+  - "LITELLM_PROXY_API_KEY"
+patterns:
+  - regex: 'sk-[A-Za-z0-9_\-]{20,}'
+    entropy_min: 4.0
+    confidence: low
+verify:
+  method: GET
+  url: ""
+  headers: {}
+  valid_status: []
+  invalid_status: []