fix(usage): account for cache-write tokens across schema versions

Parse cache_write_tokens from OpenAI usage details and preserve cache creation data across Chat, Responses, and Anthropic conversion paths.

Add explicit input-token semantics to request logs and rollups so legacy rows subtract cache reads only while new total-inclusive rows subtract both cache reads and writes. Migrate v12 databases, normalize rollups to fresh input, and cover historical backfill behavior with regression tests.

src-tauri/src/proxy/providers/transform.rs

@@ -665,7 +665,7 @@ pub fn openai_to_anthropic(body: Value) -> Result<Value, ProxyError> {
     // 不再扣减），若不减则缓存会被计入 input 与各 cache 桶两次。三桶互斥，恒等：
     // input + cache_read + cache_creation == prompt_tokens（inclusive 上游）。
     // 与流式 build_anthropic_usage_json (#2774) 及 transform_gemini 的 saturating_sub 对称。
-    // 最终 cache_read：直传字段优先于 nested；cache_creation 仅来自直传字段（OpenAI 无此概念）。
+    // 最终 cache_read/cache_creation：直传字段优先于 OpenAI nested details。
     let cached = usage
         .get("cache_read_input_tokens")
         .and_then(|v| v.as_u64())
@@ -678,6 +678,12 @@ pub fn openai_to_anthropic(body: Value) -> Result<Value, ProxyError> {
     let cache_creation = usage
         .get("cache_creation_input_tokens")
         .and_then(|v| v.as_u64())
+        .or_else(|| {
+            usage
+                .pointer("/prompt_tokens_details/cache_write_tokens")
+                .or_else(|| usage.pointer("/input_tokens_details/cache_write_tokens"))
+                .and_then(|v| v.as_u64())
+        })
         .unwrap_or(0);
     let input_tokens = usage
         .get("prompt_tokens")