feat: SMS fallback refactor - user-controllable filters/limits/balance

New user options:
- Content filter: important-only (default) or forward-all
- Rate limit: toggle on/off, adjustable minutes
- Balance check: toggle on/off (off = no suspend, no decrement)

UI: SMS section now has 3 SwitchRows under target list, with
balance/carrier/quota status + "解除挂起" button shown when
balance check is on.

Logic: SmsFallbackForwarder reads new flags to skip checks;
CarrierBalanceQuery guards decrement/suspend on flag.

version 1.9.9 -> 1.10.0 (code 38 -> 39)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/build.gradle.kts

@@ -13,8 +13,8 @@ android {
         applicationId = "com.a2i.forwarder"
         minSdk = 34
         targetSdk = 36
-        versionCode = 38
-        versionName = "1.9.9"
+        versionCode = 39
+        versionName = "1.10.0"
     }
 
     signingConfigs {