refactor!: rename module to github.com/theirongolddev/cburn

Change module path from 'cburn' to 'github.com/theirongolddev/cburn'
to enable standard Go remote installation:

  go install github.com/theirongolddev/cburn@latest

This is a BREAKING CHANGE for any external code importing this module
(though as a CLI tool, this is unlikely to affect anyone).

All internal imports updated to use the new module path.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

main.go

@@ -1,7 +1,7 @@
 // cburn analyzes Claude Code usage from local JSONL session logs.
 package main
 
-import "cburn/cmd"
+import "github.com/theirongolddev/cburn/cmd"
 
 func main() {
 	cmd.Execute()