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/pages/inventory.html

@@ -0,0 +1,43 @@
+{{define "content"}}
+<div class="inventory-shell d-flex">
+  <aside id="tree-pane" class="tree-pane border-end d-flex flex-column">
+    <div class="p-2 border-bottom">
+      <div class="input-group input-group-sm mb-2">
+        <span class="input-group-text"><i class="bi bi-search"></i></span>
+        <input type="search" id="tree-search" class="form-control" placeholder="Search inventory&hellip;">
+      </div>
+      <div class="d-flex gap-1 flex-wrap">
+        <button class="btn btn-sm btn-outline-secondary" id="btn-expand-all" title="Expand all folders"><i class="bi bi-arrows-expand"></i> Expand</button>
+        <button class="btn btn-sm btn-outline-secondary" id="btn-collapse-all" title="Collapse all folders"><i class="bi bi-arrows-collapse"></i> Collapse</button>
+        {{if .User.IsAdmin}}
+        <button class="btn btn-sm btn-primary ms-auto" id="btn-new-root-folder" data-parent-id="" title="New top-level folder">
+          <i class="bi bi-folder-plus"></i>
+        </button>
+        {{end}}
+      </div>
+    </div>
+    <div class="tree-scroll flex-fill overflow-auto">
+      <ul class="tree list-unstyled mb-0" id="tree-root">
+        <li class="tree-node tree-node-root" data-type="root">
+          <div class="tree-row selected" data-type="root" tabindex="0">
+            <span class="tree-toggle-spacer"></span>
+            <i class="bi bi-house-door-fill tree-icon text-primary"></i>
+            <span class="tree-label">Inventory</span>
+          </div>
+        </li>
+        <li>
+          <ul class="tree-children list-unstyled" id="top-level-children" data-expanded="true">
+            {{template "tree_children" .Tree}}
+          </ul>
+        </li>
+      </ul>
+    </div>
+  </aside>
+
+  <section id="main-panel" class="main-panel flex-fill overflow-auto" data-context-type="root" data-context-id="">
+    {{template "panel_root" .Root}}
+  </section>
+</div>
+
+{{template "modals" .}}
+{{end}}