feat: configurable media quality via config.json

Add a `media_quality` section to config.json that allows self-hosters
to configure video codec, resolution, bitrate, framerate, and simulcast
layers for both camera and screen sharing.

This addresses the long-standing request in #249 for configurable media
quality settings. The LiveKit SDK already supports all of these options;
this change exposes them through the existing config system.

New config.json fields:
- media_quality.video_codec: preferred codec (vp8/vp9/h264/av1)
- media_quality.video: camera resolution, bitrate, framerate, simulcast layers
- media_quality.screen_share: screen share resolution, bitrate, framerate,
  simulcast layers (enables 3+ layer simulcast for screen sharing)

All fields are optional and fall back to the existing defaults (VP8,
720p camera, 1080p screen share) when not specified.

Signed-off-by: Ryan Emmick <ryanemmick4@gmail.com>

src/state/CallViewModel/localMember/LocalMember.ts

@@ -12,6 +12,8 @@ import {
   type ScreenShareCaptureOptions,
   RoomEvent,
   MediaDeviceFailure,
+  type ScreenSharePreset,
+  VideoPreset as VideoPresetClass,
 } from "livekit-client";
 import { observeParticipantEvents } from "@livekit/components-core";
 import {
@@ -661,6 +663,7 @@ export const createLocalMembership$ = ({
     !getUrlParams().hideScreensharing
   ) {
     toggleScreenSharing = (): void => {
+      const screenConf = Config.get().media_quality?.screen_share;
       const screenshareSettings: ScreenShareCaptureOptions = {
         // Screen share audio shouldn't have any filtering.
         // "echoCancellation" is purposely excluded, as setting it to
@@ -674,6 +677,13 @@ export const createLocalMembership$ = ({
         selfBrowserSurface: "include",
         surfaceSwitching: "include",
         systemAudio: "include",
+        ...(screenConf?.max_resolution && {
+          resolution: {
+            width: Math.round((screenConf.max_resolution * 16) / 9),
+            height: screenConf.max_resolution,
+            frameRate: screenConf.max_framerate ?? 30,
+          },
+        }),
       };
       const targetScreenshareState = !sharingScreen$.value;
       logger.info(

src/state/CallViewModel/remoteMembers/ConnectionFactory.ts

@@ -27,7 +27,10 @@ import type {
 import type { MediaDevices } from "../../MediaDevices.ts";
 import type { Behavior } from "../../Behavior.ts";
 import type { ProcessorState } from "../../../livekit/TrackProcessorContext.tsx";
-import { defaultLiveKitOptions } from "../../../livekit/options.ts";
+import {
+  defaultLiveKitOptions,
+  getLiveKitOptions,
+} from "../../../livekit/options.ts";
 
 // TODO evaluate if this should be done like the Publisher Factory
 export interface ConnectionFactory {
@@ -138,15 +141,16 @@ function generateRoomOption({
   echoCancellation: boolean;
   noiseSuppression: boolean;
 }): RoomOptions {
+  const liveKitOptions = getLiveKitOptions();
   return {
-    ...defaultLiveKitOptions,
+    ...liveKitOptions,
     videoCaptureDefaults: {
-      ...defaultLiveKitOptions.videoCaptureDefaults,
+      ...liveKitOptions.videoCaptureDefaults,
       deviceId: devices.videoInput.selected$.value?.id,
       processor: processorState.processor,
     },
     audioCaptureDefaults: {
-      ...defaultLiveKitOptions.audioCaptureDefaults,
+      ...liveKitOptions.audioCaptureDefaults,
       deviceId: devices.audioInput.selected$.value?.id,
       echoCancellation,
       noiseSuppression,