Rework Update UI and fix banch

CHANGELOG.md

@@ -69,6 +69,10 @@ Only this release needs the command line for the database update. Normal updates
 - Settings > Ticketing: the email-to-ticket hint no longer names a cron script that has not existed for several releases, and points at Maintenance > Cron instead.
 - Setup: the command line installer now prints the crontab entry and the reminder to turn cron on, the same two steps the web installer shows on its finish page.
 - Removed the unused `config_invoice_overdue_reminders` setting. It was seeded on install and read in two places but never actually used by anything; the overdue reminder schedule is fixed in the nightly job.
+- Update page: reworked. Release, tracked branch, database version and code commit are now shown whatever state the install is in, instead of only when it is already up to date, and a pending database update no longer hides a pending application update — both appear, in the order they need doing. Pending commits are listed in a readable table rather than a centred one, and the backup warning is stated once instead of twice.
+- Update page: **Force Update no longer resets to `origin/master` regardless of the branch you track.** On an install following any other branch it silently moved the files onto master and discarded the code that was actually running. It now resets to the branch in `$repo_branch`, and so does `update_cli.php --force_update`. Installs with no `$repo_branch` in `config.php` still get master, as before.
+- Update page: the database update is now offered using a proper version comparison. The old string comparison would have stopped offering updates once a version reached a two-digit part — `2.6.10` sorts below `2.6.9` as plain text.
+- Update page: Git output — commit subjects and error text — is escaped before it reaches the page, and the branch name is escaped before it reaches a shell command. The page also no longer runs a second `git fetch` just to read the error message from the first one.
 - Cron: the nightly run is safe to repeat. Late fees, overdue invoice reminders and autopay retries now apply at most once per invoice per day, so a Run Now after the scheduled pass no longer stacks fees or re-emails clients. Nightly Tasks only accepts the daily schedule.
 - Ticket SLAs, optional throughout. An SLA sets a response target and an optional resolution target, assigned per client and priority with a global default and an explicit "no SLA" override. Targets are measured against your business hours. Tickets show time remaining and turn yellow at a configurable warning threshold and red on breach, on both the ticket list and the kanban board, and can be filtered by SLA state. Nominated statuses pause the resolution clock for "waiting on customer", preserving the remaining budget. Two new reports, SLA Summary and SLA by Client. With no assignments defined nothing behaves any differently.
 - Ticket: added an Urgent priority.