Added package install manifests for split binary packages so files previously left in debian/tmp are assigned to the correct outputs:

zoitechat-common (desktop integration, dbus service, icons, locales, appdata, mime).
    zoitechat-dev (plugin development header + pkg-config file).
    zoitechat-lua, zoitechat-perl, zoitechat-plugins, and zoitechat-python3 (plugin/shared module payloads).
Simplified zoitechat.install to only the core executable + man page, with shared data moved to zoitechat-common to match package split intent.

debian/zoitechat-common.install

@@ -0,0 +1,7 @@
+usr/share/applications/net.zoite.Zoitechat.desktop
+usr/share/dbus-1/services/org.zoitechat.service.service
+usr/share/icons/hicolor/48x48/apps/net.zoite.Zoitechat.png
+usr/share/icons/hicolor/scalable/apps/net.zoite.Zoitechat.svg
+usr/share/locale/*/LC_MESSAGES/zoitechat.mo
+usr/share/metainfo/net.zoite.Zoitechat.appdata.xml
+usr/share/mime/packages/net.zoite.Zoitechat.mime.xml

debian/zoitechat-dev.install

@@ -0,0 +1,2 @@
+usr/include/zoitechat-plugin.h
+usr/lib/*/pkgconfig/zoitechat-plugin.pc

debian/zoitechat-lua.install

@@ -0,0 +1 @@
+usr/lib/*/zoitechat/plugins/lua.so

debian/zoitechat-perl.install

@@ -0,0 +1 @@
+usr/lib/*/zoitechat/plugins/perl.so

debian/zoitechat-plugins.install

@@ -0,0 +1,3 @@
+usr/lib/*/zoitechat/plugins/checksum.so
+usr/lib/*/zoitechat/plugins/fishlim.so
+usr/lib/*/zoitechat/plugins/sysinfo.so

debian/zoitechat-python3.install

@@ -0,0 +1,4 @@
+usr/lib/*/zoitechat/plugins/python.so
+usr/lib/*/zoitechat/python/_zoitechat.py
+usr/lib/*/zoitechat/python/xchat.py
+usr/lib/*/zoitechat/python/zoitechat.py

debian/zoitechat.install

@@ -1,5 +1,2 @@
 usr/bin/zoitechat
-usr/share/applications
 usr/share/man/man1/zoitechat.1
-usr/share/metainfo/net.zoite.Zoitechat.appdata.xml
-usr/share/mime/packages/net.zoite.Zoitechat.mime.xml