fix: ntfy use JSON publish API (raw body was treated as attachment)

ntfy.sh now treats any request body (PUT/POST, text/plain) as a file
attachment, so messages never showed in the app. Switch to ntfy's JSON
publish API: POST / with {topic,title,message}.

version 1.7.1 -> 1.7.2 (code 14 -> 15)

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

app/src/main/java/com/a2i/forwarder/core/NtfySender.kt

@@ -10,11 +10,13 @@ import okhttp3.OkHttpClient
 import okhttp3.Request
 import okhttp3.MediaType.Companion.toMediaType
 import okhttp3.RequestBody.Companion.toRequestBody
+import org.json.JSONObject
 import java.io.IOException
 import java.util.concurrent.TimeUnit
 
 /**
- * ntfy 推送：POST {server}/{topic}，可选 Bearer auth。
+ * ntfy 推送：用 JSON publish API（POST / with {topic,title,message}）。
+ * 注：raw body 会被 ntfy 当附件，必须用 JSON API 或 Message header。
  * 对瞬时 IOException 自动重试 3 次（退避 600/1200ms）。
  */
 object NtfySender {
@@ -30,13 +32,15 @@ object NtfySender {
         title: String, body: String,
     ): Result<Unit> = withContext(Dispatchers.IO) {
         runCatching {
-            val url = server.trim().removeSuffix("/") + "/" + topic.trim()
-            val req = Request.Builder().url(url)
-                .header("Title", title.take(200))
-                .apply {
-                    if (token.isNotBlank()) header("Authorization", "Bearer $token")
-                }
-                .put(body.take(4000).toRequestBody(TEXT_PLAIN))
+            val payload = JSONObject()
+                .put("topic", topic.trim())
+                .put("title", title.take(200))
+                .put("message", body.take(4000))
+                .toString()
+            val req = Request.Builder()
+                .url(server.trim().removeSuffix("/"))
+                .apply { if (token.isNotBlank()) header("Authorization", "Bearer $token") }
+                .post(payload.toRequestBody(JSON))
                 .build()
             doPushWithRetry(req)
         }
@@ -68,7 +72,7 @@ object NtfySender {
         }
     }
 
-    private val TEXT_PLAIN = "text/plain; charset=utf-8".toMediaType()
+    private val JSON = "application/json; charset=utf-8".toMediaType()
     private const val MAX_ATTEMPTS = 3
     private val BACKOFF_MS = longArrayOf(600L, 1200L)
 }