Summary

Adds compact Previous (◀) and Next (▶) chevron buttons to the action bar of these edit pages, so users can walk from one record to the next without bouncing back to the list page:

• Extensions
• Destinations
• Dialplan Manager
• Inbound Routes
• Outbound Routes
• Devices
• Follow Me (call_forward)

A small n / N position indicator sits next to the arrows. Keyboard shortcuts Alt+◀ / Alt+▶ also navigate (ignored while typing in a form field).

Why

When triaging, onboarding or auditing it is common to open record after record from a filtered list. The current flow forces list → edit → save → back → next row → edit for every single record. This PR lets the user just keep clicking ▶ after each Save.

The navigation follows the exact list the user last saw on the list page — including the current search filter, order_by / order sort, page, and (where applicable) the Show All cross-domain view.

Implementation

• New auto-loaded helper class resources/classes/edit_nav.php with two static methods (snapshot() and render()).
• Each list page calls edit_nav::snapshot() once, immediately after fetching its rows, which stores the ordered list of uuids in $_SESSION['edit_nav'][<module_key>] (one extra line per list page).
• Each edit page calls edit_nav::render() inside the action bar, which returns the prev / next / position HTML, or '' when there is no fresh snapshot (one small block per edit page, right after the existing Save button).
• Snapshots have a 1-hour TTL guard so we never navigate via ancient state.
• The Dialplan Manager, Inbound Routes and Outbound Routes views are keyed separately by app_uuid, so switching between them never clobbers each other's snapshots.
• 100% server-side PHP — no JavaScript framework, no theme modifications, no sessionStorage. The only inline <script> is a 12-line keydown handler for the Alt+Arrow shortcuts.

Backwards compatibility

Strictly additive. Users who deep-link straight to an edit page (bookmarks, new session, no list visited yet) see no change at all, because edit_nav::render() returns an empty string when no snapshot exists. No new permissions, no new settings, no schema change, no new language strings.

Scope

• 1 new file: resources/classes/edit_nav.php (~190 lines, auto-loaded)
• 10 existing files touched, 3 lines added per file on average

Manual test plan

1. Visit any list page above — page loads as before.
2. Click into a record — ◀ ▶ 3 / 47 appears in the action bar after Save.
3. Click ▶ — navigates to the next record in the same sort order, preserving the list-page search/sort.
4. Bookmark an edit URL directly, open it in a fresh session — arrows are not rendered (graceful no-op).
5. Press Alt+◀ / Alt+▶ while focused outside any form field — navigates.