install (pyproject): Remove dbus-python and make pygobject optional:

`dbus-python` is no longer used since the D-Bus bridge is now fully based on txdbus.

As a consequence, `pygobject` is no longer necessary for base features, but still
necessary for webRTC-based features (as we are using GStreamer). Making it optional makes
the installation far easier, as the GLib parts often cause trouble during installation
(mainly because they need local libraries).

pyproject.toml

@@ -25,7 +25,6 @@ dependencies = [
     "alembic",
     "babel < 3",
     "cryptography >= 41.0.1",
-    "dbus-python < 1.3",
     "emoji ~= 2.8",
     "html2text < 2020.2",
     "jinja2 >= 3.1.2",
@@ -43,7 +42,6 @@ dependencies = [
     "pydantic ~= 2.12",
     "pydantic-settings ~= 2.12",
     "pygments < 3",
-    "pygobject ~= 3.48",
     "pyopenssl ~= 24.1",
     "python-dateutil >= 2.8.1, < 3",
     # currently disabled due to incompatibility, OTR feature may be removed in
@@ -90,7 +88,11 @@ GUI = [
 TUI = [
     "term-image ~= 0.7.1"
 ]
+webrtc = [
+    "pygobject >= 3.48",
+]
 remote-control = [
+    "libervia-backend[webrtc]",
     "cbor2"
 ]
 conferences = [
@@ -120,6 +122,9 @@ all = [
     "libervia-backend[GUI]",
     # Only used for (real) images in terminal.
     "libervia-backend[TUI]",
+    # Necessary for A/V calls and webRTC based file transfer in local frontends
+    # (i.e.; everything but web).
+    "libervia-backend[webrtc]",
     # Following 2 are experimental
     "libervia-backend[remote-control]",
     "libervia-backend[conferences]",