fix: allow campaign processor to work without fallback sender when using mining sources (OAuth)

- Remove blocking requirement for fallback sender at processor start
- Fallback sender is now optional - processor will use mining sources per campaign
- Keep fallback sender check for email-sending-request notification endpoint

Author: baderdean

supabase/functions/email-campaigns/index.ts

@@ -1796,26 +1796,26 @@ app.post(
   async (c: Context) => {
     const supabaseAdmin = createSupabaseAdmin();
     let fallbackSenderEmail = "";
-    if (!isFallbackSenderEnabled()) {
-      return c.json(
-        {
-          error: "Fallback sender is disabled",
-          code: "FALLBACK_SENDER_DISABLED",
-        },
-        500,
-      );
-    }
-    try {
-      fallbackSenderEmail = requireFallbackSenderEmail();
-    } catch (error) {
-      return c.json(
-        {
-          error: extractErrorMessage(error),
-          code: "SMTP_SENDER_NOT_CONFIGURED",
-        },
-        500,
+
+    // Allow processing without fallback sender if campaigns use mining sources (OAuth)
+    if (isFallbackSenderEnabled()) {
+      try {
+        fallbackSenderEmail = requireFallbackSenderEmail();
+      } catch (error) {
+        logger.warn(
+          "Fallback sender not configured, will use mining sources per campaign",
+          {
+            error: extractErrorMessage(error),
+          },
+        );
+        fallbackSenderEmail = "";
+      }
+    } else {
+      logger.info(
+        "Fallback sender disabled, will use mining sources per campaign",
       );
     }
+
     const dayStart = getTodayUtcStartString();
     const processingDeadline = Date.now() + PROCESSING_DEADLINE_MS;
     logger.debug("Starting campaign processing", {