Initial implementation of inventree

A small IT asset inventory system built around a nested folder tree,
matching the project brief: Go + html/template + Bootstrap 5 + vanilla JS,
SQLite storage (WAL, FKs, migrations), embedded templates/static assets,
single compiled binary.

- AJAX-driven inventory tree: lazy-loaded folder expansion with per-user
  persisted expand state, drag-and-drop move for folders/assets, safe
  delete-with-relocate-or-cascade confirmation, search with breadcrumbs.
- Assets: CRUD, duplicate, move, auto-generated IT-000001-style IDs,
  CSV import (with optional folder auto-create) and export.
- Admin-defined item types with custom fields (text/long_text/number/date/
  boolean/dropdown/url/ip_address).
- Configurable statuses, session-based auth (bcrypt, secure cookies),
  admin/user roles, user management.
- CLI: serve, version, database migrate, database backup; /healthz;
  graceful shutdown; Dockerfile/docker-compose/systemd unit; Go test suite.

web/templates/partials/tree_children.html

@@ -0,0 +1,44 @@
+{{define "tree_children"}}
+{{range .}}
+  {{if eq .Type "folder"}}
+  <li class="tree-node" data-type="folder" data-id="{{.ID}}" draggable="true">
+    <div class="tree-row" data-type="folder" data-id="{{.ID}}" tabindex="0">
+      {{if .HasChildren}}
+      <button type="button" class="tree-toggle{{if .Expanded}} expanded{{end}}" data-id="{{.ID}}" aria-label="Toggle">
+        <i class="bi bi-chevron-right"></i>
+      </button>
+      {{else}}
+      <span class="tree-toggle-spacer"></span>
+      {{end}}
+      <i class="bi {{iconOr .Icon "bi-folder-fill"}} tree-icon text-warning-emphasis"></i>
+      <span class="tree-label">{{.Name}}</span>
+      <span class="tree-actions admin-only">
+        <button type="button" class="btn-tree-action" data-action="menu" data-id="{{.ID}}" data-type="folder" title="Actions">
+          <i class="bi bi-three-dots"></i>
+        </button>
+      </span>
+    </div>
+    <ul class="tree-children list-unstyled{{if not .Expanded}} d-none{{end}}" data-expanded="{{.Expanded}}" data-loaded="{{.Expanded}}">
+      {{if .Expanded}}{{template "tree_children" .Children}}{{end}}
+    </ul>
+  </li>
+  {{else if eq .Type "asset"}}
+  <li class="tree-node" data-type="asset" data-id="{{.ID}}" draggable="true">
+    <div class="tree-row" data-type="asset" data-id="{{.ID}}" tabindex="0">
+      <span class="tree-toggle-spacer"></span>
+      <i class="bi {{iconOr .Icon "bi-box-seam"}} tree-icon text-body-secondary"></i>
+      <span class="tree-label">{{.Name}}</span>
+      <span class="badge rounded-pill text-bg-{{.StatusColor}} tree-status-badge">{{.StatusName}}</span>
+    </div>
+  </li>
+  {{else}}
+  <li class="tree-node tree-node-more">
+    <div class="tree-row tree-row-more text-body-secondary fst-italic">
+      <span class="tree-toggle-spacer"></span>
+      <i class="bi bi-three-dots"></i>
+      <span class="tree-label">{{.Name}}</span>
+    </div>
+  </li>
+  {{end}}
+{{end}}
+{{end}}