chore(release): bump to 0.9.1 (stable)

rc1 verified on phone: home Wi-Fi attach under active VPN triggers the
rule engine through the new underlying-network bridge, both directions
(away→VPN on, home→VPN off) work in real-world walks. Drop -rc suffix
so CI picks APP_ENV=stable and the install loses the PRE corner ribbon.

Author: oviron

pubspec.yaml

@@ -1,7 +1,7 @@
 name: fl_clash
 description: Android mihomo client. Open source, no ads, no telemetry.
 publish_to: 'none'
-version: 0.9.1-rc1+2026051401
+version: 0.9.1+2026051402
 environment:
   sdk: '>=3.8.0 <4.0.0'