Rename project from inventree to vibetree

- go.mod module path (and every internal/vibetree import) inventree -> vibetree
- cmd/inventree/ -> cmd/vibetree/, deploy/inventree.service -> vibetree.service
- Default site name (seed data + the siteName template func's fallback)
  is now "vibetree", shown in the navbar, <title>, and login page
- Session cookie renamed inventree_session -> vibetree_session
- Default DB path data/inventree.db -> data/vibetree.db, CLI/log text,
  Dockerfile, docker-compose.yml, README, .gitignore/.dockerignore all
  updated to match

Existing installs: this changes the session cookie name (users will be
signed out once) and the default DB filename (point -db at your existing
file, or rename it, to keep your data).

internal/web/router.go

@@ -3,10 +3,10 @@ package web
 import (
 	"net/http"
 
-	content "inventree/web"
+	content "vibetree/web"
 )
 
-// Router builds the complete HTTP handler for inventree: static assets,
+// Router builds the complete HTTP handler for vibetree: static assets,
 // authentication, the AJAX-driven inventory tree, and the traditional
 // full-page admin sections (item types, users, settings).
 func (a *App) Router() http.Handler {