Phase 3: Go hygiene pass, runtime PUID/PGID, fork README

Go:
- staticcheck 399 -> 0 with staticcheck.conf (style checks ST1000/1003/
  1005/1016/1020/1021/1022 excluded; error strings are shown in the UI).
- io/ioutil and rand.Seed removed; CloseNotifier kept with a lint-ignore
  until the Phase 2 context rewrite.
- Dead code deleted: Auto handler, getStreamByChannelID, updateXEPG,
  indexOfInt, jsonToMapInt64, removeOldSystemData, randomTime, and the
  commented-out blocks in struct-buffer.go and internal/authentication.
- Duplicates folded: cacheImagesInBackground(), one addErrorToStream().
- Bugs found by SA4006/SA5001: os.Create handle leaked per ffmpeg segment
  (buffer.go), http.NewRequest error unchecked (buffer.go), xepg.json
  migration wrote null on read error (migrate.go), WriteUserData errors
  silently dropped (authentication.go), defer Close before error check
  (buffer.go, toolchain.go). checkFilePermission results were discarded;
  an unwritable config or temp dir is now fatal at start-up.
- gofmt applied repo-wide; Drone runs gofmt check and staticcheck.

Docker:
- Entrypoint starts as root, applies PUID/PGID (falls back to XTEVE_UID/
  XTEVE_GID, then image defaults), fixes config ownership only when it
  differs, then drops to xteve via su-exec. --user starts skip all of it.
- /xteve removed from LEGACY_CONFIG_DIRS (it is the parent of the default).
- mwader/static-ffmpeg pinned to 7.1.1; VOLUME /xteve/config.
- Compose files pull registry.coadcorp.com/nathan/xteve:latest, use
  PUID/PGID/TZ, and explain that SSDP needs host networking.
- .dockerignore excludes the npm toolchain (bundle stays in html/js).

Docs: README rewritten for the fork (about, registry, compose, env vars,
security notes); README-DEV gains a container section.

src/struct-webserver.go

@@ -3,7 +3,7 @@ package src
 // RequestStruct : Anfragen über die Websocket Schnittstelle
 type RequestStruct struct {
 	// Befehle an xTeVe
-	Cmd string `json:"cmd,required"`
+	Cmd string `json:"cmd"`
 
 	// Benutzer
 	DeleteUser bool           `json:"deleteUser,omitempty"`
@@ -79,46 +79,46 @@ type ResponseStruct struct {
 		DVR       string `json:"DVR"`
 		EpgSource string `json:"epgSource"`
 		Errors    int    `json:"errors"`
-		M3U       string `json:"m3u-url,required"`
+		M3U       string `json:"m3u-url"`
 		OS        string `json:"os"`
 		Streams   string `json:"streams"`
 		UUID      string `json:"uuid"`
 		Version   string `json:"version"`
 		Warnings  int    `json:"warnings"`
 		XEPGCount int64  `json:"xepg"`
-		XML       string `json:"xepg-url,required"`
+		XML       string `json:"xepg-url"`
 	} `json:"clientInfo"`
 
 	Data struct {
 		Playlist struct {
 			M3U struct {
 				Groups struct {
-					Text  []string `json:"text,required"`
-					Value []string `json:"value,required"`
-				} `json:"groups,required"`
-			} `json:"m3u,required"`
-		} `json:"playlist,required"`
+					Text  []string `json:"text"`
+					Value []string `json:"value"`
+				} `json:"groups"`
+			} `json:"m3u"`
+		} `json:"playlist"`
 
 		StreamPreviewUI struct {
-			Active   []string `json:"activeStreams,required"`
-			Inactive []string `json:"inactiveStreams,required"`
+			Active   []string `json:"activeStreams"`
+			Inactive []string `json:"inactiveStreams"`
 		}
-	} `json:"data,required"`
+	} `json:"data"`
 
 	Alert               string             `json:"alert,omitempty"`
-	ConfigurationWizard bool               `json:"configurationWizard,required"`
+	ConfigurationWizard bool               `json:"configurationWizard"`
 	Error               string             `json:"err,omitempty"`
-	Log                 WebScreenLogStruct `json:"log,required"`
+	Log                 WebScreenLogStruct `json:"log"`
 	LogoURL             string             `json:"logoURL,omitempty"`
 	OpenLink            string             `json:"openLink,omitempty"`
 	OpenMenu            string             `json:"openMenu,omitempty"`
 	Reload              bool               `json:"reload,omitempty"`
-	Settings            SettingsStruct     `json:"settings,required"`
-	Status              bool               `json:"status,required"`
+	Settings            SettingsStruct     `json:"settings"`
+	Status              bool               `json:"status"`
 	Token               string             `json:"token,omitempty"`
 	Users               map[string]any     `json:"users,omitempty"`
 	Wizard              int                `json:"wizard,omitempty"`
-	XEPG                map[string]any     `json:"xepg,required"`
+	XEPG                map[string]any     `json:"xepg"`
 
 	Notification map[string]Notification `json:"notification,omitempty"`
 }
@@ -135,7 +135,7 @@ type APIRequestStruct struct {
 type APIResponseStruct struct {
 	EpgSource     string `json:"epg.source,omitempty"`
 	Error         string `json:"err,omitempty"`
-	Status        bool   `json:"status,required"`
+	Status        bool   `json:"status"`
 	StreamsActive int64  `json:"streams.active,omitempty"`
 	StreamsAll    int64  `json:"streams.all,omitempty"`
 	StreamsXepg   int64  `json:"streams.xepg,omitempty"`
@@ -149,7 +149,7 @@ type APIResponseStruct struct {
 
 // WebScreenLogStruct : Logs werden im RAM gespeichert und für das Webinterface bereitgestellt
 type WebScreenLogStruct struct {
-	Errors   int      `json:"errors,required"`
-	Log      []string `json:"log,required"`
-	Warnings int      `json:"warnings,required"`
+	Errors   int      `json:"errors"`
+	Log      []string `json:"log"`
+	Warnings int      `json:"warnings"`
 }