feat(stats): count emails forwarded to the catch-all fallback

Adds an emails_forwarded counter (a subset of emails_rejected) bumped on a
successful FALLBACK_FORWARD_ADDRESS forward. Dropped = rejected − forwarded.
Surfaced in the /api/v1/stats response and the public status page.

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

src/routes/api/schemas.ts

@@ -138,6 +138,7 @@ export const StatsSchema = z
     feeds_deleted: z.number(),
     emails_received: z.number(),
     emails_rejected: z.number(),
+    emails_forwarded: z.number(),
     unsubscribes_sent: z.number(),
     active_feeds: z.number(),
     websub_subscriptions_active: z.number(),

src/routes/home.tsx

@@ -162,6 +162,10 @@ export async function handle(c: Context<{ Bindings: Env }>): Promise<Response> {
               value={stats.emails_rejected}
               tone="danger"
             />
+            <Stat
+              label="Forwarded (catch-all)"
+              value={stats.emails_forwarded}
+            />
             <Stat
               label="Acceptance rate"
               value={acceptanceRate}