feat(api-logs): persist response body on failed external calls

ApiLogger now stores the upstream response body to
`api_logs.response_body` whenever the call failed (non-2xx response or
a RequestException carrying a response). Successful 2xx responses
remain null so the table stays small on busy services like fuel:poll
and oil:fetch.

Truncated at 64 KB. The column is mediumText so a future cap raise
needs no schema change.

Captures:
- 4xx and 5xx response bodies verbatim
- Body extracted from RequestException via `$e->response->body()`
  when callers use `Http::throw()`

Does not capture:
- ConnectionException (no response existed)
- Generic Throwable from the closure (same reason)

Motivation: the LLM overlay's "skipped — no verified citations" path
left no forensic trail to debug. With this, the next time anything
routed through ApiLogger fails — Anthropic 429s, FRED 5xx, Fuel
Finder errors — the failed body is queryable directly:

    SELECT response_body FROM api_logs
    WHERE service = ? AND status_code >= 400
    ORDER BY id DESC LIMIT 1;

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/Models/ApiLog.php

@@ -7,7 +7,7 @@ use Illuminate\Database\Eloquent\Attributes\Fillable;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
 
-#[Fillable(['service', 'method', 'url', 'status_code', 'duration_ms', 'error'])]
+#[Fillable(['service', 'method', 'url', 'status_code', 'duration_ms', 'error', 'response_body'])]
 class ApiLog extends Model
 {
     /** @use HasFactory<ApiLogFactory> */