chore(vscode): fix Linux paths in the task and launch configs

The "go: build" task hardcoded bin/3x-ui.exe, so building on Linux
produced a binary carrying a Windows extension. It now emits bin/3x-ui
and keeps the .exe name behind a windows override.

The Postgres launch config prepended C:\Program Files\PostgreSQL\18\bin
to PATH on every platform. Linux separates entries with ':', not ';', so
that string fused into the first real PATH entry and clobbered it. Moved
it into a windows block, which is where the pg_dump/pg_restore lookups
in ServerService need it anyway.

.vscode/tasks.json

@@ -8,9 +8,17 @@
       "args": [
         "build",
         "-o",
-        "bin/3x-ui.exe",
+        "bin/3x-ui",
         "./main.go"
       ],
+      "windows": {
+        "args": [
+          "build",
+          "-o",
+          "bin/3x-ui.exe",
+          "./main.go"
+        ]
+      },
       "options": {
         "cwd": "${workspaceFolder}"
       },