feat(qoder): port Kiro-style provider integration with COSY signing

Replaces the Qoder placeholder with a real free-tier provider:

- Device-flow OAuth: PKCE + nonce generated locally, user authorizes at
  qoder.com/device/selectAccounts, poll openapi.qoder.sh until token
- COSY signing (RSA-1024 + AES-128-CBC + MD5) for chat / model-list
- WAF-bypass body encoding (custom-alphabet base64 + thirds rearrange)
- Live model_config catalog from /algo/api/v2/model/list, cached 1h
- 11 models registered (auto/ultimate/performance/efficient/lite +
  6 frontier *model ids)
- Usage fetcher for openapi.qoder.sh/api/v2/quota/usage
- Dashboard live-models resolver, provider test, OAuth modal hookup
- 24 unit tests covering encoder, PKCE, COSY headers, sigPath stripping

open-sse/config/providerModels.js

@@ -144,6 +144,21 @@ export const PROVIDER_MODELS = {
     { id: "claude-sonnet-4.5-thinking-agentic", name: "Claude Sonnet 4.5 (Thinking + Agentic)" },
     { id: "claude-haiku-4.5-thinking-agentic", name: "Claude Haiku 4.5 (Thinking + Agentic)" },
   ],
+  qd: [  // Qoder AI - tier + frontier models (server-published catalog)
+    // Tier models — pick a quality/cost tradeoff
+    { id: "auto", name: "Qoder Auto" },
+    { id: "ultimate", name: "Qoder Ultimate" },
+    { id: "performance", name: "Qoder Performance" },
+    { id: "efficient", name: "Qoder Efficient" },
+    { id: "lite", name: "Qoder Lite" },
+    // Frontier models — pin a specific backing model
+    { id: "qmodel", name: "Qwen 3.6 Plus (Qoder)" },
+    { id: "dmodel", name: "DeepSeek V4 Pro (Qoder)" },
+    { id: "dfmodel", name: "DeepSeek V4 Flash (Qoder)" },
+    { id: "gm51model", name: "GLM 5.1 (Qoder)" },
+    { id: "kmodel", name: "Kimi K2.6 (Qoder)" },
+    { id: "mmodel", name: "MiniMax M2.7 (Qoder)" },
+  ],
   cu: [  // Cursor IDE
     { id: "default", name: "Auto (Server Picks)" },
     { id: "claude-4.5-opus-high-thinking", name: "Claude 4.5 Opus High Thinking" },
@@ -870,6 +885,7 @@ const OAUTH_ALIASES = {
   kilocode: "kc",
   cline: "cl",
   opencode: "oc",
+  qoder: "qd",
   vertex: "vertex",
   "vertex-partner": "vertex-partner",
 };