feat(usage): surface Gemini thinkingConfig as reasoning effort

Usage records show a reasoning badge next to the model name for OpenAI and
Claude requests, but Gemini requests never got one. The extraction only read
the OpenAI/Claude shapes (`reasoning_effort`, `reasoning.effort`,
`output_config.effort`), while Gemini states its reasoning depth inside
`generationConfig.thinkingConfig` — so nothing was written to the usage
metadata and the list and detail views had no badge to render.

Read the Gemini shape too, as a fallback after the existing three so the
OpenAI and Claude paths are untouched:

- `thinkingLevel` / `thinking_level` wins when present, trimmed and
  lowercased, with the protobuf enum prefix stripped so `THINKING_LEVEL_HIGH`
  resolves like `high`.
- Otherwise `thinkingBudget` / `thinking_budget` goes through the existing
  shared budget ladder, yielding the same `low|medium|high|xhigh` vocabulary
  the badge already understands.
- Both camelCase and snake_case spellings are read, so a captured client body
  and a converted provider body resolve to the same label.
- `includeThoughts` alone is a visibility flag, not a depth, and produces no
  badge.

Two cases are handled explicitly rather than through the shared ladder:

- `thinkingBudget: 0` disables reasoning outright. The shared ladder maps
  `0..=1664` to `low`, which would report an explicitly disabled request as a
  shallow one, so it reports `none` instead.
- `THINKING_LEVEL_UNSPECIFIED` is the enum's "no explicit level" member, not a
  depth; it is rejected rather than surfaced as an `unspecified` badge.

The frontend needs no change: `UsageModelDisplay` already renders the badge
whenever the fields are present, and keeps the `high -> xhigh` mapping format
when the requested and upstream efforts differ.

apps/aether-gateway/src/handlers/public/support/user_me_usage.rs

@@ -1905,6 +1905,29 @@ mod tests {
         assert_eq!(active["reasoning_effort"], "max");
     }
 
+    #[test]
+    fn user_usage_payloads_expose_gemini_thinking_config_reasoning_mapping() {
+        let item = StoredRequestUsageAudit {
+            request_body: Some(json!({
+                "generationConfig": {
+                    "thinkingConfig": { "includeThoughts": true, "thinkingLevel": "HIGH" }
+                }
+            })),
+            provider_request_body: Some(json!({
+                "generationConfig": { "thinkingConfig": { "thinkingBudget": 8192 } }
+            })),
+            ..sample_usage("completed")
+        };
+
+        let record = build_users_me_usage_record_payload(&item, false, &BTreeMap::new(), false);
+        let active = build_users_me_usage_active_payload(&item);
+
+        assert_eq!(record["requested_reasoning_effort"], "high");
+        assert_eq!(active["requested_reasoning_effort"], "high");
+        assert_eq!(record["reasoning_effort"], "xhigh");
+        assert_eq!(active["reasoning_effort"], "xhigh");
+    }
+
     #[test]
     fn user_usage_payloads_expose_websocket_transport() {
         let item = StoredRequestUsageAudit {