fix: accept invitation page returning a 404 (resolves #1804)

[jobara]

Resolves #1804

Corrects the fallback route to the landing page.

Prerequisites

If this PR changes PHP code or dependencies:

• I've run composer format and fixed any code formatting issues.
• I've run composer analyze and addressed any static analysis issues.
• I've run php artisan test and ensured that all tests pass.
• I've run composer localize to update localization source files and committed any changes.

If this PR changes CSS or JavaScript code or dependencies:

• I've run npm run lint and fixed any linting issues.
• I've run npm run build and ensured that CSS and JavaScript assets can be compiled.

[codecov]

Codecov Report

Merging #1821 (5b50f96) into dev (6dc89fe) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##                dev    #1821   +/-   ##
=========================================
  Coverage     96.47%   96.47%           
  Complexity     1984     1984           
=========================================
  Files           299      299           
  Lines          8636     8636           
=========================================
  Hits           8332     8332           
  Misses          304      304           

Impacted Files	Coverage Δ
app/Providers/RouteServiceProvider.php	94.44% <ø> (ø)