Implement media storage and processing features: update configuration in .env.example and appsettings files, enhance Docker setup for media storage, and add media-related services and database entities. Include ffmpeg for media handling and adjust Kestrel settings for large file uploads.

backend/src/TeleWave.Api/appsettings.json

@@ -13,6 +13,19 @@
     "Username": "",
     "Password": ""
   },
+  "Storage": {
+    "RootPath": "/media",
+    "SegmentSeconds": 2,
+    "KeepOriginals": false,
+    "MinFreeSpaceBytes": 10737418240
+  },
+  "Media": {
+    "FfmpegPath": "ffmpeg",
+    "FfprobePath": "ffprobe",
+    "MaxUploadBytes": 21474836480,
+    "TranscodeThreads": 3,
+    "InboxScanSeconds": 15
+  },
   "Serilog": {
     "Using": [ "Serilog.Sinks.Console" ],
     "MinimumLevel": {