feat: add "transcode configurations" (#1001)

This adds the notion of creating and maintaining transcode
configurations. This is a generalization of the current ffmpeg settings
flow. Users can edit various settings relating to transcoding in each
config and then assign a configuration to a channel. This allows for
more fine-grained customization of transcoding per-channel and also
allows for users to test new configurations without affecting the global
state of Tunarr.

types/src/TranscodeConfig.ts

@@ -0,0 +1,4 @@
+import { z } from 'zod';
+import { TranscodeConfigSchema } from './schemas/transcodeConfigSchemas.js';
+
+export type TranscodeConfig = z.infer<typeof TranscodeConfigSchema>;