feat(search): add structured filters to AI session list endpoint and frontend

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/api/aiSessions.ts

@@ -43,8 +43,23 @@ export const aiSessionsApi = {
     return response.data
   },
 
-  async listSessions(params?: { status?: string; skip?: number; limit?: number }): Promise<AISessionSummary[]> {
-    const response = await apiClient.get<AISessionSummary[]>('/ai-sessions', { params })
+  async listSessions(params?: {
+    status?: string
+    skip?: number
+    limit?: number
+    problem_domain?: string
+    matched_flow_id?: string
+    confidence_tier?: string
+    ticket_id?: string
+    date_from?: string
+    date_to?: string
+    q?: string
+  }): Promise<AISessionSummary[]> {
+    // Strip empty string values so they aren't sent as empty query params
+    const cleanParams = params
+      ? Object.fromEntries(Object.entries(params).filter(([, v]) => v !== '' && v !== undefined))
+      : undefined
+    const response = await apiClient.get<AISessionSummary[]>('/ai-sessions', { params: cleanParams })
     return response.data
   },