feat(03-01): add 8 Tier 4 providers (Baichuan, StepFun, SenseTime, iFlytek, Tencent, SiliconFlow, 360AI, Kuaishou)

- SiliconFlow uses documented sk- prefix
- Other 7 keyword-only (no documented key format, avoids false positives)
- Completes PROV-04: 16 Tier 4 Chinese/regional providers

providers/iflytek.yaml

@@ -0,0 +1,19 @@
+format_version: 1
+name: iflytek
+display_name: iFlytek Spark (讯飞星火)
+tier: 4
+last_verified: "2026-04-05"
+keywords:
+  - "iflytek"
+  - "xf_yun"
+  - "spark_desk"
+  - "XFYUN_API_KEY"
+  - "XFYUN_API_SECRET"
+  - "XFYUN_APPID"
+  - "spark-api.xf-yun.com"
+verify:
+  method: GET
+  url: ""
+  headers: {}
+  valid_status: []
+  invalid_status: []