feat(pricing): add ~50 new model pricing entries and fix outdated prices

Add pricing data for 4 new providers (Qwen, xAI Grok, Mistral, Cohere)
and supplement existing providers (MiniMax M2.5/M2.7, GLM-5/5.1,
Doubao Seed 2.0, MiMo V2 Pro, OpenAI o1/o3/codex-mini/gpt-5-mini/nano).

Fix outdated prices for deepseek-chat, deepseek-reasoner, and kimi-k2.5.
Fix display_name casing "Mimo" → "MiMo" for consistency.

Use prepared statement in seed_model_pricing() to avoid recompiling SQL
on each of ~130 INSERT iterations.

Schema migration v8→v9: DELETE + re-seed model_pricing for existing users.

src-tauri/src/database/mod.rs

@@ -44,7 +44,7 @@ use std::sync::Mutex;
 
 /// 当前 Schema 版本号
 /// 每次修改表结构时递增，并在 schema.rs 中添加相应的迁移逻辑
-pub(crate) const SCHEMA_VERSION: i32 = 8;
+pub(crate) const SCHEMA_VERSION: i32 = 9;
 
 /// 安全地序列化 JSON，避免 unwrap panic
 pub(crate) fn to_json_string<T: Serialize>(value: &T) -> Result<String, AppError> {