install.bat: fix parens-in-username breaking OTP path expansion (#1826)

On Windows, when %USERPROFILE% contains parentheses (e.g.
`PeterLinder(3Txpert)`), four lines in install.bat fail because
%tmp_dir% expands inside `if (...)` cmd-batch blocks at parse time —
the embedded close-paren terminates the if-block early, producing
"syntactisch nicht verarbeitbar" / "syntactically unprocessable"
errors before the OTP download even begins.

Two complementary fixes match the existing patterns:

- Quote the path argument in curl.exe / del (lines 148, 205) — the
  Elixir-side curl at line 192 was already correctly quoted; this
  restores symmetry with the OTP-side calls.
- Use delayed expansion `!tmp_dir!\!otp_zip!` (lines 150, 194) — both
  are inside if-blocks where %tmp_dir% would expand at parse time.
  Delayed expansion expands at execution time, after the parser has
  already matched the if-block parens.

Verified locally on a Windows account with parenthesized username:
unpatched `install.bat elixir@latest otp@latest` fails before OTP
download; patched version completes both downloads cleanly.

Author: hanuele

install.bat

@@ -145,9 +145,9 @@ if not exist "%otp_dir%\bin" (
 
   set otp_url=https://github.com/erlang/otp/releases/download/OTP-!otp_version!/%otp_zip%
   echo downloading !otp_url!...
-  curl.exe -fsSLo %tmp_dir%\%otp_zip% "!otp_url!" || exit /b 1
+  curl.exe -fsSLo "%tmp_dir%\%otp_zip%" "!otp_url!" || exit /b 1
 
-  echo unpacking %tmp_dir%\%otp_zip%
+  echo unpacking !tmp_dir!\!otp_zip!
   powershell -NoProfile -Command ^
     "$ErrorActionPreference='Stop';" ^
     "try {" ^
@@ -191,7 +191,7 @@ if not exist "%elixir_dir%\bin" (
   echo downloading !elixir_url!...
   curl.exe -fsSLo "%tmp_dir%\%elixir_zip%" "!elixir_url!" || exit /b 1
 
-  echo unpacking %tmp_dir%\%elixir_zip%
+  echo unpacking !tmp_dir!\!elixir_zip!
   powershell -NoProfile -Command ^
     "$ErrorActionPreference='Stop';" ^
     "try {" ^
@@ -202,6 +202,6 @@ if not exist "%elixir_dir%\bin" (
     "    Expand-Archive -LiteralPath '%tmp_dir%\%elixir_zip%' -DestinationPath '%elixir_dir%' -Force" ^
     "  }" ^
     "} catch { Write-Error $_; exit 1 }"
-  del /f /q %tmp_dir%\%elixir_zip%
+  del /f /q "%tmp_dir%\%elixir_zip%"
 )
 goto :eof