Split view, personal modes, budget warnings, server move script

- Up to three chats side by side (#/s/a+b+c), "Open beside" in the sidebar menu
- File manager tabs of a chat stored per user on the server (/sessions/{id}/tabs)
- Personal modes for every user (Settings → My modes, /account/modes)
- Budget meters (total, provider, images, opencode Go windows) with push warnings
  for admins at the warning share and 100 %, shown in the status overlay
- scripts/move-server.sh: move to another Docker host with bind mounts (Unraid);
  scripts/smoke-test.sh

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -3,6 +3,23 @@
 All notable changes to CodeCraft. Versions follow [Semantic Versioning](https://semver.org/);
 until 1.0, minor versions may contain breaking changes.
 
+## [Unreleased]
+
+### Added
+
+- **Chats side by side:** *Open beside* in a chat's sidebar menu shows up to three chats as
+  columns, each with its own tabs and composer (desktop).
+- **My modes:** every user can create personal modes under *Settings → My modes* (kind, tools,
+  read-only, prompt, model); they appear only for that user.
+- **Budget warnings** as push notifications for admins (warning share and 100 %) for the total,
+  provider and image budgets and the opencode Go windows; the status overlay shows all budgets.
+- `scripts/move-server.sh` moves an installation to another Docker host with bind mounts
+  (e.g. Unraid), `scripts/smoke-test.sh` checks a running instance.
+
+### Changed
+
+- File manager tabs of a chat are stored on the server, so they are the same on every device.
+
 ## [v202611-00003] – 2026-11-09
 
 ### Added