Add typed account and password settings

- Add admin account list, create, role, delete, and password workflows
- Execute identity-checked mutations through the existing dispatcher
- Bound queued credential lifetime and wipe transient secrets
- Add explicit password generation with saved-value acknowledgement
- Handle self-revocation and uncertain outcomes without automatic
  retries
- Register optional account routes without disrupting terminal
  transports
- Expand host regressions and document contracts and pending target
  checks

Validated host suites and pio run; hardware validation remains pending.

tests/web_cookie_auth/test.c

@@ -1,7 +1,13 @@
 /* Production store dependency doubles and its existing public API suite. */
 #define main store_tests
+#ifdef HOST_ACCOUNTS
+#define user_database_username_valid store_username_valid
+#endif
 #include "../web_session_store/test.c"
 #undef main
+#ifdef HOST_ACCOUNTS
+#undef user_database_username_valid
+#endif
 #include "web_cookie_auth.h"
 #include "web_httpd_adapter.h"
 #include "esp_httpd_priv.h"
@@ -126,6 +132,9 @@ static void auth_reset(void) {
 #ifdef HOST_SERIAL_SETTINGS
 #include "serial_settings_test.c"
 #endif
+#ifdef HOST_ACCOUNTS
+#include "account_settings_test.c"
+#endif
 
 int main(void) {
     assert(store_tests() == 0); auth_reset();
@@ -279,6 +288,9 @@ int main(void) {
 #endif
 #ifdef HOST_SERIAL_SETTINGS
     serial_settings_tests();
+#endif
+#ifdef HOST_ACCOUNTS
+    account_settings_tests();
 #endif
     return 0;
 }