[AI] Route AI calls through the Xray/V2Ray proxy (reach OpenAI from Iran)

Add AiUseProxy setting + a toggle in the AI settings section. ScrapeHttpClients.ForAi(settings) returns a proxied HttpClient (reusing IngestProxyUrl, 100s timeout) when AiUseProxy is on, otherwise direct; AI-cache keys are protected from the scrape-client cleanup. OpenAiCompatibleAuditor now uses it, so the AI auditor (e.g. api.openai.com) is reachable through the same Xray sidecar that serves Telegram. Migration adds the column.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/JobsMedical.Web/Models/AppSetting.cs

@@ -32,6 +32,10 @@ public class AppSetting
     /// <summary>If AI approves AND Mode is Automatic, publish without human review.</summary>
     public bool AiAutoApprove { get; set; } = false;
 
+    /// <summary>Route AI calls through the ingestion proxy (IngestProxyUrl) — needed when the AI
+    /// endpoint (e.g. api.openai.com) is blocked in Iran.</summary>
+    public bool AiUseProxy { get; set; } = false;
+
     // --- Channel scraping sources (configured here, NOT in env) ---
     /// <summary>Run the ingestion worker on a timer.</summary>
     public bool AutoIngestEnabled { get; set; } = false;