Upgrade default Claude Opus model to 4.8

Bump the default Opus route/model from claude-opus-4-7 to claude-opus-4-8
across provider presets (claude, claudeDesktop, hermes, openclaw, opencode,
universal), i18n locales (zh/en/ja/zh-TW), pricing seed data, and the
user-manual docs.

- Add claude-opus-4-8 pricing row ($5/$25/$0.50/$6.25); keep the 4-7 row
  for historical usage stats (seeded via INSERT OR IGNORE).
- Claude Desktop proxy: accept bidirectional opus 4-7 <-> 4-8 route alias
  during rollout so previously saved routes keep resolving.
- thinking_optimizer: route opus-4-8 through adaptive thinking and normalize
  dotted model ids (also fixes dotted 4-6/4-7 falling back to legacy).
- usage_stats: normalize Bedrock/Vertex/aggregator opus-4-8 ids to base
  pricing.

Also merge role:"system" messages into the Gemini systemInstruction in the
Anthropic->Gemini transform.

src-tauri/src/deeplink/provider.rs

@@ -805,7 +805,7 @@ mod tests {
             name: Some("MyHermes".to_string()),
             endpoint: Some("https://api.example.com/v1".to_string()),
             api_key: Some("sk-test".to_string()),
-            model: Some("anthropic/claude-opus-4-7".to_string()),
+            model: Some("anthropic/claude-opus-4-8".to_string()),
             ..Default::default()
         }
     }
@@ -827,7 +827,7 @@ mod tests {
         // models array with the deeplink model id
         let models = obj.get("models").unwrap().as_array().unwrap();
         assert_eq!(models.len(), 1);
-        assert_eq!(models[0]["id"], "anthropic/claude-opus-4-7");
+        assert_eq!(models[0]["id"], "anthropic/claude-opus-4-8");
     }
 
     #[test]