feat(deepseek): switch presets to V4 (flash/pro) and add pricing

DeepSeek released V4 flash/pro; legacy IDs deepseek-chat / deepseek-reasoner
now alias to deepseek-v4-flash and will be deprecated.

- Update claude/hermes/opencode/openclaw presets to v4-pro / v4-flash,
  context 128K -> 1M; Claude Anthropic-compat endpoint routes OPUS/SONNET
  to v4-pro and HAIKU to v4-flash, plus an explicit modelsUrl override.
- Seed deepseek-v4-flash ($0.14/$0.28 per 1M) and deepseek-v4-pro
  ($1.68/$3.36 per 1M) into model_pricing; older v3.x / chat / reasoner
  rows kept for historical usage stats (INSERT OR IGNORE).
- Refresh user-manual (zh/en/ja) pricing table and note that legacy model
  IDs are billed at v4-flash rates.

src-tauri/src/database/schema.rs

@@ -1620,6 +1620,23 @@ impl Database {
                 "0.14",
                 "0",
             ),
+            // DeepSeek V4 系列（官方 CNY 按 1 USD ≈ 7.14 折算）
+            (
+                "deepseek-v4-flash",
+                "DeepSeek V4 Flash",
+                "0.14",
+                "0.28",
+                "0.028",
+                "0",
+            ),
+            (
+                "deepseek-v4-pro",
+                "DeepSeek V4 Pro",
+                "1.68",
+                "3.36",
+                "0.14",
+                "0",
+            ),
             // Kimi (月之暗面)
             (
                 "kimi-k2-thinking",