fix(usage): pricing routing, SSE lifecycle, and validation hardening

* model pricing routing: extend prefix-match families (gpt-/o1-o5/
  gemini-/deepseek-/qwen-/glm-/kimi-/minimax-) with per-family dash
  thresholds so short base IDs like gpt-5 no longer mis-match
  gpt-5-mini; strip ISO and 8-digit date suffixes via UTF-8-safe
  byte matching so claude-haiku-4-5-20251001 falls back to
  claude-haiku-4-5 pricing
* SSE collector: SseUsageFinishGuard (RAII) guarantees finish() on
  early return or panic; AtomicBool fast path lets push() skip the
  Mutex once first-event time is recorded
* validation: shared validate_cost_multiplier / validate_pricing_source
  helpers across DAO and service layers; PRICING_SOURCE_RESPONSE /
  PRICING_SOURCE_REQUEST constants replace string literals; price
  fields in update_model_pricing now reject empty / non-decimal /
  negative input before INSERT
* backfill: add backfill_missing_usage_costs_for_model so a single
  price edit only scans matching rows instead of the full log table;
  startup backfill remains full-scan
* session_usage{,_codex,_gemini}: share find_model_pricing helper from
  usage_stats; metadata_modified_nanos centralizes mtime precision
* frontend: NON_NEGATIVE_DECIMAL_REGEX + isNonNegativeDecimalString
  replace three copies of the same multiplier regex; isUnpricedUsage
  surfaces zero-cost rows that have usage tokens (cached per row to
  avoid double evaluation); invalidate usageKeys.all on pricing mutate
  so backfilled rows refresh

src-tauri/src/database/dao/proxy.rs

@@ -2,12 +2,56 @@
 //!
 //! 处理代理配置、Provider健康状态和使用统计的数据库操作
 
+use std::str::FromStr;
+
 use crate::error::AppError;
 use crate::proxy::types::*;
 use rust_decimal::Decimal;
 
 use super::super::{lock_conn, Database};
 
+pub(crate) const PRICING_SOURCE_RESPONSE: &str = "response";
+pub(crate) const PRICING_SOURCE_REQUEST: &str = "request";
+
+pub(crate) fn validate_cost_multiplier(value: &str) -> Result<Decimal, AppError> {
+    let trimmed = value.trim();
+    if trimmed.is_empty() {
+        return Err(AppError::localized(
+            "error.multiplierEmpty",
+            "倍率不能为空",
+            "Multiplier cannot be empty",
+        ));
+    }
+    let parsed = Decimal::from_str(trimmed).map_err(|e| {
+        AppError::localized(
+            "error.invalidMultiplier",
+            format!("无效倍率: {value} - {e}"),
+            format!("Invalid multiplier: {value} - {e}"),
+        )
+    })?;
+    if parsed < Decimal::ZERO {
+        return Err(AppError::localized(
+            "error.invalidMultiplier",
+            format!("无效倍率: {value} - 倍率不能为负数"),
+            format!("Invalid multiplier: {value} - multiplier cannot be negative"),
+        ));
+    }
+    Ok(parsed)
+}
+
+pub(crate) fn validate_pricing_source(value: &str) -> Result<&str, AppError> {
+    let trimmed = value.trim();
+    if trimmed == PRICING_SOURCE_RESPONSE || trimmed == PRICING_SOURCE_REQUEST {
+        Ok(trimmed)
+    } else {
+        Err(AppError::localized(
+            "error.invalidPricingMode",
+            format!("无效计费模式: {value}"),
+            format!("Invalid pricing mode: {value}"),
+        ))
+    }
+}
+
 impl Database {
     // ==================== Global Proxy Config ====================
 
@@ -103,21 +147,8 @@ impl Database {
         app_type: &str,
         value: &str,
     ) -> Result<(), AppError> {
+        validate_cost_multiplier(value)?;
         let trimmed = value.trim();
-        if trimmed.is_empty() {
-            return Err(AppError::localized(
-                "error.multiplierEmpty",
-                "倍率不能为空",
-                "Multiplier cannot be empty",
-            ));
-        }
-        trimmed.parse::<Decimal>().map_err(|e| {
-            AppError::localized(
-                "error.invalidMultiplier",
-                format!("无效倍率: {value} - {e}"),
-                format!("Invalid multiplier: {value} - {e}"),
-            )
-        })?;
 
         // 确保行存在
         self.ensure_proxy_config_row_exists(app_type)?;
@@ -150,7 +181,7 @@ impl Database {
             Ok(value) => Ok(value),
             Err(rusqlite::Error::QueryReturnedNoRows) => {
                 self.init_proxy_config_rows().await?;
-                Ok("response".to_string())
+                Ok(PRICING_SOURCE_RESPONSE.to_string())
             }
             Err(e) => Err(AppError::Database(e.to_string())),
         }
@@ -162,14 +193,7 @@ impl Database {
         app_type: &str,
         value: &str,
     ) -> Result<(), AppError> {
-        let trimmed = value.trim();
-        if !matches!(trimmed, "response" | "request") {
-            return Err(AppError::localized(
-                "error.invalidPricingMode",
-                format!("无效计费模式: {value}"),
-                format!("Invalid pricing mode: {value}"),
-            ));
-        }
+        let trimmed = validate_pricing_source(value)?;
 
         // 确保行存在
         self.ensure_proxy_config_row_exists(app_type)?;
@@ -911,6 +935,18 @@ mod tests {
             }
         ));
 
+        let err = db
+            .set_default_cost_multiplier("claude", "-0.5")
+            .await
+            .unwrap_err();
+        assert!(matches!(
+            err,
+            AppError::Localized {
+                key: "error.invalidMultiplier",
+                ..
+            }
+        ));
+
         Ok(())
     }
 }

src-tauri/src/database/mod.rs

@@ -33,6 +33,10 @@ mod tests;
 
 // DAO 类型导出供外部使用
 pub(crate) use dao::providers_seed::CLAUDE_DESKTOP_OFFICIAL_PROVIDER_ID;
+pub(crate) use dao::proxy::{
+    validate_cost_multiplier, validate_pricing_source, PRICING_SOURCE_REQUEST,
+    PRICING_SOURCE_RESPONSE,
+};
 pub use dao::FailoverQueueItem;
 
 use crate::config::get_app_config_dir;