Remove test client creation functionality from admin extension

Client registration will now be handled by the DCA client extension.
The admin extension focuses solely on:
- Reading existing clients
- Managing deposits (pending → confirmed workflow)
- Monitoring DCA activity

Test client creation code preserved in 'feature/test-client-creation' branch.

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

templates/satmachineadmin/index.html

@@ -95,15 +95,6 @@
               <q-icon name="info" color="orange" />
             </template>
             No DCA clients registered yet. Clients must first install and configure the DCA client extension.
-            <template v-slot:action>
-              <q-btn 
-                flat 
-                color="orange" 
-                label="Create Test Client" 
-                @click="createTestClient"
-                size="sm"
-              />
-            </template>
           </q-banner>
         </div>