feat(email): forward non-feed mail to FALLBACK_FORWARD_ADDRESS

Lets you point a domain's catch-all at the worker without losing personal
mail: inbound mail that isn't a feed (invalid_address / feed_not_found) is
forwarded to an optional verified destination instead of being dropped.
Expired feeds and blocked senders are still dropped so newsletters never
leak to the fallback inbox. Unset env keeps the original drop-and-log path.

Co-Authored-By: Claude Opus 4.7 <[email protected]>

wrangler-example.toml

@@ -47,6 +47,12 @@ DOMAIN = "REPLACE_WITH_YOUR_DOMAIN" # Web domain (used for feed URLs and admin U
 # the admin UI is pre-filled and read-only. Remove to allow per-feed configuration.
 # FEED_TTL_HOURS = "24"
 
+# Optional: catch-all fallback forwarding. Inbound mail that isn't a feed (bad
+# address or unknown feed) is forwarded here instead of dropped — lets you point
+# a domain's catch-all at this worker without losing personal mail. The address
+# MUST be a *verified* destination in Cloudflare Email Routing or forwarding fails.
+# FALLBACK_FORWARD_ADDRESS = "[email protected]"
+
 # Optional: external proxy auth (Authelia/Authentik)
 # Comma-separated IPs of trusted reverse proxies
 # PROXY_TRUSTED_IPS = "10.0.0.1"