fix: prevent username input from unmounting during typing in login form

The username input was conditionally hidden when it had a value, causing
the field to disappear and focus to jump to password when typing. Fixed by:
1. Always rendering the username input (removed conditional)
2. Using controlled input with value prop
3. Only auto-focus password when username is already entered

This fixes the focus-jumping bug that made it impossible to enter usernames.

.claude/settings.local.json

@@ -85,7 +85,11 @@
       "Bash(grep -E \"\\\\.\\(py|ts\\)$\")",
       "Bash(grep -E \"\\\\.py$\")",
       "Bash(git worktree *)",
-      "Bash(npm list *)"
+      "Bash(npm list *)",
+      "Bash(netstat -tulpn)",
+      "Bash(curl -k -v https://192.168.84.131:8918/users/)",
+      "Bash(curl -k -s https://192.168.84.131:8918/users/)",
+      "Bash(grep -E \"\\\\.\\(tsx|ts|jsx|js\\)$\")"
     ]
   }
 }