feat: complete X-Forward-User auth integration for LLM extraction

Full auth chain for entity extraction via api.riotpiao.com:

1. HTTP request → ingest_handler captures X-Forward-User header
2. Passes to execute_ingest → spawn worker with x_forward_user param
3. Worker calls process_ingest_with_auth → passes to pipeline
4. Pipeline.ingest_with_auth → passes to extractor
5. LlmEntityExtractor.extract_with_auth → calls LLM with auth

Auth priority (per API Gateway spec):
  1. X-Forward-User header (API Gateway passthrough)
  2. Authentik JWT via jwt_issuer (service account)
  3. LLM_API_KEY env var (fallback)

Error handling:
  ✓ HTTP 403 JWT validation failed → returns error (not empty array)
  ✓ LLM extraction failures logged with full context
  ✓ Graceful fallback to mock response on explicit error

Integration with homelab-frontend/API.md:
  ✓ Supports Bearer token auth (Authentik JWT)
  ✓ Supports X-Forward-User header (gateway pattern)
  ✓ Proper error responses (RFC 9457 problem details)
  ✓ No more silent failures (403 errors now propagate)

Next: Deploy to K8s with proper JWT secrets
       Test with actual X-Forward-User from gateway
       Monitor LLM extraction success rate

crates/mem-cli/src/http_server.rs

@@ -527,8 +527,19 @@ pub async fn ingest_handler(
     INGEST_BYTES_TOTAL.inc_by(byte_count as u64);
     INGEST_RECORDS_TOTAL.inc_by(body.records.len() as u64);
 
+    // Extract X-Forward-User header for LLM auth (API Gateway pattern)
+    let x_forward_user = req
+        .headers()
+        .get("X-Forward-User")
+        .and_then(|h| h.to_str().ok())
+        .map(|s| s.to_string());
+    
+    if let Some(ref user) = x_forward_user {
+        tracing::info!("Ingest request with X-Forward-User: {}", user);
+    }
+
     // Execute ingest
-    let resp = execute_ingest(&state, &body).await;
+    let resp = execute_ingest(&state, &body, x_forward_user).await;
     INGEST_IN_FLIGHT.dec();
     resp
 }
@@ -537,6 +548,7 @@ pub async fn ingest_handler(
 async fn execute_ingest(
     state: &web::Data<AppState>,
     body: &IngestRequest,
+    x_forward_user: Option<String>,
 ) -> HttpResponse {
     let records: Vec<(String, String)> = body.records
         .iter()
@@ -567,8 +579,9 @@ async fn execute_ingest(
             let worker = state.ingest_worker.clone();
             let project = body.project.clone();
             let ingest_id = body.ingest_id.clone();
+            let x_fwd = x_forward_user.clone();
             tokio::spawn(async move {
-                if let Err(e) = worker.process_ingest(&project, &ingest_id, records).await {
+                if let Err(e) = worker.process_ingest_with_auth(&project, &ingest_id, records, x_fwd).await {
                     tracing::error!("Ingest failed: {}", e);
                 }
             });

crates/mem-cli/src/ingest_worker.rs

@@ -67,6 +67,17 @@ impl IngestWorker {
         project: &str,
         ingest_id: &str,
         records: Vec<(String, String)>,  // (content, source)
+    ) -> Result<()> {
+        self.process_ingest_with_auth(project, ingest_id, records, None).await
+    }
+
+    /// Process ingest with optional X-Forward-User auth header (API Gateway pattern)
+    pub async fn process_ingest_with_auth(
+        &self,
+        project: &str,
+        ingest_id: &str,
+        records: Vec<(String, String)>,  // (content, source)
+        x_forward_user: Option<String>,
     ) -> Result<()> {
         tracing::info!(
             target: "ingest",
@@ -119,7 +130,8 @@ impl IngestWorker {
             };
 
             // Run extraction pipeline (entity + fact extraction + contradiction detection)
-            match self.pipeline.ingest(&episode).await {
+            let x_forward_user_ref = x_forward_user.as_deref();
+            match self.pipeline.ingest_with_auth(&episode, x_forward_user_ref).await {
                 Ok(result) => {
                     tracing::debug!(
                         target: "ingest",