feat: wire external rules pipeline into ingress and dispatch

- Add DispatchContext field to Task model for rule metadata storage
- Add BlocklistEmails config (BLOCKLIST_EMAILS env var)
- Wire rules.Pipeline into IMAPWatcher, replacing inline whitelist check
- Pass rule metadata through DispatchContext to OpenClaw dispatch
- Remove isWhitelisted method (now handled by WhitelistRule)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/ai_client/client.go

@@ -73,7 +73,7 @@ func (d *Dispatcher) Dispatch(task *database.Task) {
 		SessionID:   task.ThreadID,
 		History:     history,
 		CallbackURL: callbackURL,
-		Metadata:    map[string]string{"task_uuid": task.TaskUUID},
+		Metadata:    buildDispatchMetadata(task),
 	}
 
 	// Update status to AI_PROCESSING before first attempt.
@@ -195,3 +195,18 @@ func (d *Dispatcher) buildHistory(threadID string) ([]historyEntry, error) {
 
 	return history, nil
 }
+
+// buildDispatchMetadata constructs the metadata map for OpenClaw dispatch,
+// merging the task UUID with any DispatchContext from the rules pipeline.
+func buildDispatchMetadata(task *database.Task) map[string]string {
+	metadata := map[string]string{"task_uuid": task.TaskUUID}
+	if task.DispatchContext != "" {
+		var ctx map[string]string
+		if err := json.Unmarshal([]byte(task.DispatchContext), &ctx); err == nil {
+			for k, v := range ctx {
+				metadata[k] = v
+			}
+		}
+	}
+	return metadata
+}