Fix: store KWallet passwords via D-Bus (kwallet-query -w never persists)

kwallet-query --write-password returns success but does not create the folder
or persist the secret, so saved host passwords were silently lost and share
enumeration failed with NT_STATUS_LOGON_FAILURE. Write/delete now go through
the kwalletd6 D-Bus API via qdbus6 (open/createFolder/writePassword). Reads
stay on kwallet-query (they work). Also drop smbclient -N (was forcing an
anonymous session) and silence KWallet read stderr. Adds qt6-tools dep.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

README.md

@@ -25,7 +25,8 @@ Install these with your distribution's package manager:
 | `mount.cifs`     | `cifs-utils`           | mount CIFS shares                |
 | `smbclient`      | `smbclient`            | list shares on a host            |
 | `pkexec`         | `polkit`               | authorize the mount helper       |
-| `kwallet-query`  | `kwallet` (KF6)        | store/read passwords in KWallet  |
+| `kwallet-query`  | `kwallet` (KF6)        | read passwords from KWallet      |
+| `qdbus6`         | `qt6-tools`            | write passwords to KWallet (D-Bus) |
 | `findmnt`        | `util-linux`           | detect mounted shares            |
 
 On Debian/Ubuntu the equivalents are `plasma-workspace`, `cifs-utils`,