feat: add new user accounts and direct certificate download link to manual

- Add three new user accounts: admin_uibk, julia_steiner, and summitwave_general
- Add direct download link for summitwave-beacon.crt certificate in manual
- Provide alternative download method alongside existing browser-based certificate retrieval

src/manual/auth.config.php

@@ -8,5 +8,8 @@ return [
         'summitwave_malte'            => 'M8uN3fZq!c2Lx9Pt',
         'summitwave_patrick'          => 'S4rK7vBw#h1Dz6Qe',
         'ellerbrock_konferenztechnik' => 'E9pL2mTy@k5Vg8Rs',
+        'admin_uibk'                  => 'U7bK4nWx#j3Fp9Ct',
+        'julia_steiner'               => 'J5sT8mRq@v2Lh6Yd',
+        'summitwave_general'          => 'G3nR9kPw!e1Bz4Xm',
     ],
 ];