fix: redirect early CLI console logger to stderr

When running `gitea dump` with output routed to stdout (--file -),
deprecation warnings from loadAvatarsFrom were written to stdout,
corrupting the archive stream.

Root cause: PrepareConsoleLoggerLevel (called in app.Before) sets up
a console logger via SetConsoleLogger, which used WriterConsoleOption{}
defaulting Stderr to false (i.e. stdout). This logger is installed before
the dump subcommand can redirect logging to stderr in runDump.

Fix: use WriterConsoleOption{Stderr: true} in SetConsoleLogger so all
early CLI diagnostic output goes to stderr from the start. This is correct
for all subcommands — diagnostic/log output should never pollute stdout.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: tht

modules/log/logger_global.go

@@ -80,7 +80,7 @@ func SetConsoleLogger(loggerName, writerName string, level Level) {
 		Level:        level,
 		Flags:        FlagsFromBits(LstdFlags),
 		Colorize:     CanColorStdout,
-		WriterOption: WriterConsoleOption{},
+		WriterOption: WriterConsoleOption{Stderr: true},
 	})
 	GetManager().GetLogger(loggerName).ReplaceAllWriters(writer)
 }