feat: Widen the Pro banner rotation and split it by role

The banner still advertised the calendar, recurring cards and guest roles —
features from 2.3 — to everyone who ran an instance. It now carries nine
features up to 2.5.0, and the ten strings behind them sit in their
alphabetical place rather than in the middle of the two-factor block, where
the first three had ended up.

Who sees what now depends on the role. An admin can put a trial on their own
server today and a board user cannot, so admins get the trial line and land
on planka.app/trial while everyone else gets the overview on /pro. The
landing path is also what tells the two groups apart in the referral figures,
since nothing is measured in the app.

A full pass through nine features takes over two minutes, longer than most
visits, and the rotation restarted at the first entry on every load. The tail
of the list would have advertised nothing. The list now starts at an offset
picked per visit, which spreads the features over the visitors instead of over
the length of a session — the headline still opens every session, only the
feature that follows it varies.

The headline falls back per language. `proTrialSelfHosted` is new and exists
in two locales; `discoverPlankaPro` exists in all of them. Where the sharper
line is untranslated the softer one is used rather than a line of English, on
the one string that opens every session and fills every second slot. The link
still goes to the trial, and as translations land the check flips on its own.

The thirty-day dismissal is untouched, deliberately: any version-aware
dismissal would resurface the banner for every user at once on rollout,
because the entries already in local storage carry no version.

client/src/components/users/UserActionsStep/UserActionsStep.jsx

@@ -105,7 +105,11 @@ const UserActionsStep = React.memo(({ onClose }) => {
             })}
           </Menu.Item>
           <Menu.Item
-            href="https://planka.app/pro?ref=app-menu"
+            href={
+              withAdministration
+                ? 'https://planka.app/trial?ref=app-menu'
+                : 'https://planka.app/pro?ref=app-menu'
+            }
             target="_blank"
             rel="noopener noreferrer"
             className={styles.proMenuItem}