chore: redirect /team to /team/~ to select a team (#7124)

## [Dashboard] Fix: Simplify team redirection logic

## Notes for the reviewer
This PR modifies the team redirection logic by:
1. Renaming `getLastVisitedTeamOrDefaultTeam()` to `getLastVisitedTeam()`
2. Removing the fallback to `getDefaultTeam()` when no last visited team is found
3. Updating the team root page to redirect to `/team/~` when no team is found instead of showing a 404

## How to test
Verify that users are properly redirected to their last visited team when available, and to `/team/~` when no team history exists.

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

- **Bug Fixes**
	- Improved handling when no last visited team is found by redirecting users to a fallback page instead of showing a not found error.

- **Refactor**
	- Updated team selection logic to remove fallback to a default team and streamline user redirection.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

<!-- start pr-codex -->

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## PR-Codex overview
This PR refactors the `getLastVisitedTeamOrDefaultTeam` function to `getLastVisitedTeam`, changing its behavior to return `null` instead of a default team. It updates the `TeamRootPage` to handle the absence of a team by redirecting to a fallback URL.

### Detailed summary
- Renamed function `getLastVisitedTeamOrDefaultTeam` to `getLastVisitedTeam`.
- Changed return value of `getLastVisitedTeam` from `getDefaultTeam()` to `null`.
- Updated `TeamRootPage` to redirect to `/team/~` if no team is found, instead of calling `notFound()`.

> ✨ Ask PR-Codex anything about this PR by commenting with `/codex {your question}`

<!-- end pr-codex -->

Author: arcoraven

apps/dashboard/src/@/api/team.ts

@@ -84,7 +84,7 @@ export async function getDefaultTeam() {
   return null;
 }
 
-export async function getLastVisitedTeamOrDefaultTeam() {
+export async function getLastVisitedTeam() {
   const token = await getAuthToken();
   if (!token) {
     return null;
@@ -100,5 +100,5 @@ export async function getLastVisitedTeamOrDefaultTeam() {
     }
   }
 
-  return getDefaultTeam();
+  return null;
 }

apps/dashboard/src/app/(app)/team/page.tsx

@@ -1,10 +1,7 @@
-import { getLastVisitedTeamOrDefaultTeam } from "@/api/team";
-import { notFound, redirect } from "next/navigation";
+import { getLastVisitedTeam } from "@/api/team";
+import { redirect } from "next/navigation";
 
 export default async function TeamRootPage() {
-  const team = await getLastVisitedTeamOrDefaultTeam();
-  if (!team) {
-    notFound();
-  }
-  redirect(`/team/${team.slug}`);
+  const team = await getLastVisitedTeam();
+  redirect(team ? `/team/${team.slug}` : "/team/~");
 }