fix: resolve 6 remaining defects (P2-18, P2-21, P3-04, P3-05, P3-06, P3-02)

- P2-18: TOTP QR code local generation via qrcode lib (no external service)
- P2-21: Suspend foreign LLM providers (OpenAI/Anthropic/Gemini) for early stage
- P3-04: get_progress() now calculates actual percentage from completed/total steps
- P3-05: saveSaaSSession calls now have .catch() error logging
- P3-06: SaaS relay chatStream passes session_key/agent_id to backend
- P3-02: Whiteboard unification plan document created

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/zclaw-kernel/src/config.rs

@@ -458,6 +458,8 @@ impl KernelConfig {
                     LlmConfig::openai(api_key).with_model(model)
                 }
             }
+            // P2-21: Gemini 暂停支持 — 前期不使用非国内大模型
+            // 保留代码，但前端已标记为暂停，不再可选
             "gemini" => LlmConfig::new(
                 base_url.unwrap_or("https://generativelanguage.googleapis.com/v1beta"),
                 api_key,