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).

deploy/vibetree.service

@@ -0,0 +1,22 @@
+[Unit]
+Description=vibetree - IT asset inventory
+After=network.target
+
+[Service]
+Type=simple
+User=vibetree
+Group=vibetree
+WorkingDirectory=/opt/vibetree
+ExecStart=/opt/vibetree/vibetree serve -addr :8080 -db /opt/vibetree/data/vibetree.db
+Restart=on-failure
+RestartSec=2
+
+# Hardening (safe defaults for a small single-binary service)
+NoNewPrivileges=true
+ProtectSystem=strict
+ProtectHome=true
+ReadWritePaths=/opt/vibetree/data
+PrivateTmp=true
+
+[Install]
+WantedBy=multi-user.target