build: bump version to 1.12.14

New stable release.

Nothing too spectacular, but a various small tweaks:

- improved guix (and other systems) compatibility: make fewer assumptions about where system programs are
- documentations improvements, in manpages and the mu4e reference manual
- labels: better messages when importing
- scm: stabilize tests. tweaks api.
- mu4e: add mu4e-view-mark-and-next
- mu4e: mu4e-dbus-mode; a new experimental minor in which mu4e exposes some of
  its data over DBus.

meson.build

@@ -17,7 +17,7 @@
 ################################################################################
 # project setup
 project('mu', ['c', 'cpp'],
-        version: '1.12.14-pre5',
+        version: '1.12.14',
         meson_version: '>= 0.56.0',
         license: 'GPL-3.0-or-later',
         default_options : [
@@ -28,7 +28,7 @@ project('mu', ['c', 'cpp'],
 
 # hard-code the date here (for reproducibility); we derive the dates used in
 # e.g. documentation from this.
-mu_date='2025-12-08'
+mu_date='2025-12-20'
 
 # installation paths
 prefixdir = get_option('prefix')