feat: support new dorm area login (#1)

## Pull Request Overview

This PR enhances the login CLI to support a new “dorm area” and replaces the old `-x` flag with two new flags for server host (`-s`) and login type (`-t`).  
- Introduces a `LoginType` enum and dynamic domain/AcID mapping in `Portal`.  
- Refactors URL construction to use `go-querystring` and JSON-encoded user info.  
- Updates tests and removes the hard-coded `-x` logic in `cmd/main.go`.

### Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

<details>
<summary>Show a summary per file</summary>

| File                   | Description                                                     |
| ---------------------- | --------------------------------------------------------------- |
| portal/server_test.go  | Updated tests to supply the new `loginType` parameter and use `GetUserInfo`. |
| portal/server.go       | Reworked URL builders (`GetChallengeURL`, `GetLoginURL`), JSON `UserInfo`, and dynamic flags. |
| portal/portal.go       | Added `LoginType`, `ToDomainAcID`, updated `NewPortal`, `GetChallenge`, and `Login` signatures. |
| cmd/main.go            | Removed `-x`, added `-s`/`-t` flags, wired them through to `Portal`. |
| base64/base64.go       | Fixed typo in package comment.                                  |
| go.mod                 | Added `github.com/google/go-querystring` dependency.            |
</details>



<details>
<summary>Comments suppressed due to low confidence (4)</summary>

**base64/base64.go:1**
* Typo in the comment: 'talbe' should be 'table'.
```
// Package base64 with customized talbe
```
**portal/portal.go:53**
* New login types (`qsh-dx`, `qshd-dx`, `qshd-cmcc`) were added but there are no unit tests verifying `ToDomainAcID` returns the correct domain and AC ID for each, or that invalid types produce an error. Consider adding tests for each mapping and an invalid case.
```
func (lt LoginType) ToDomainAcID() (string, string, error) {
```
**cmd/main.go:54**
* [nitpick] The flag variables `s` and `t` are not descriptive. Consider renaming them to `server` and `loginType` (or similar) to improve clarity for users and maintainers.
```
s := flag.String("s", portal.PortalServerIPQsh, "login host")
```
**cmd/main.go:106**
* The call to `netip.ParseAddr` requires importing the `net/netip` package, but `netip` is not imported. Add `import "net/netip"` to fix the compile error.
```
_, err := netip.ParseAddr(*s)
```
</details>

---------

Co-authored-by: 源文雨 <41315874+fumiama@users.noreply.github.com>

cmd/main.go

@@ -51,7 +51,8 @@ func Main() {
 	h := flag.Bool("h", false, "display this help")
 	w := flag.Bool("w", false, "only display warn-or-higher-level log")
 	d := flag.Bool("d", false, "display debug-level log")
-	x := flag.Bool("x", false, "do dx login")
+	s := flag.String("s", portal.PortalServerIPQsh, "login host")
+	t := flag.String("t", "qsh-edu", "login type [qsh-edu | qsh-dx | qshd-dx | qshd-cmcc]")
 	flag.Parse()
 	if *h {
 		fmt.Println("Usage:")
@@ -98,27 +99,36 @@ func Main() {
 		*p = helper.BytesToString(data)
 		fmt.Println()
 	}
-	ptl, err := portal.NewPortal(*n, *p, ip)
+	logrus.Debugf("server addr: %s, login type: %s", *s, *t)
+	if *s != portal.PortalServerIPQsh {
+		// just validate IP here, 
+		// dont convert to net.IP because we need only its string later
+		_, err := netip.ParseAddr(*s)
+		if err != nil {
+			logrus.Errorln(err)
+			os.Exit(line())
+		}
+	}
+	// n : username 
+	// p: password 
+	// ip : public ip
+	// *t : login type
+	ptl, err := portal.NewPortal(*n, *p, ip, portal.LoginType(*t))
 	if err != nil {
 		logrus.Errorln(err)
 		os.Exit(line())
 	}
-	u := portal.PortalGetChallenge
-	if *x {
-		u = portal.PortalGetChallengeDX
-	}
-	challenge, err := ptl.GetChallenge(u)
+	// input:
+	// server IP
+	challenge, err := ptl.GetChallenge(*s)
 	if err != nil {
 		logrus.Errorln(err)
 		os.Exit(line())
 	}
-	u = portal.PortalLogin
-	dm := portal.PortalDomain
-	if *x {
-		u = portal.PortalLoginDX
-		dm = portal.PortalDomainDX
-	}
-	err = ptl.Login(u, dm, challenge)
+	// input: 
+	// server IP
+	// challenge
+	err = ptl.Login(*s, challenge)
 	if err != nil {
 		logrus.Errorln(err)
 		os.Exit(line())