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.

docs/user-manual/en/4-proxy/4.4-usage.md

@@ -243,6 +243,8 @@ CC Switch includes preset official prices for common models (per million tokens)
 
 | Model | Input | Output | Cache Read | Cache Creation |
 |-------|-------|--------|------------|----------------|
+| **Claude 4.8 Series** | | | | |
+| claude-opus-4-8 | $5 | $25 | $0.50 | $6.25 |
 | **Claude 4.5 Series** | | | | |
 | claude-opus-4-5 | $5 | $25 | $0.50 | $6.25 |
 | claude-sonnet-4-5 | $3 | $15 | $0.30 | $3.75 |

docs/user-manual/ja/4-proxy/4.4-usage.md

@@ -243,6 +243,8 @@ CC Switch は一般的なモデルの公式価格（100 万 Token あたり）
 
 | モデル | 入力 | 出力 | キャッシュ読取 | キャッシュ作成 |
 |------|------|------|----------|----------|
+| **Claude 4.8 シリーズ** | | | | |
+| claude-opus-4-8 | $5 | $25 | $0.50 | $6.25 |
 | **Claude 4.5 シリーズ** | | | | |
 | claude-opus-4-5 | $5 | $25 | $0.50 | $6.25 |
 | claude-sonnet-4-5 | $3 | $15 | $0.30 | $3.75 |

docs/user-manual/zh/4-proxy/4.4-usage.md

@@ -243,6 +243,8 @@ CC Switch 预设了常用模型的官方价格（每百万 Token）。v3.13.0
 
 | 模型 | 输入 | 输出 | 缓存读取 | 缓存创建 |
 |------|------|------|----------|----------|
+| **Claude 4.8 系列** | | | | |
+| claude-opus-4-8 | $5 | $25 | $0.50 | $6.25 |
 | **Claude 4.5 系列** | | | | |
 | claude-opus-4-5 | $5 | $25 | $0.50 | $6.25 |
 | claude-sonnet-4-5 | $3 | $15 | $0.30 | $3.75 |