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/panel_folder.html

@@ -0,0 +1,80 @@
+{{define "panel_folder"}}
+<div class="panel-content p-3" data-folder-id="{{.Folder.ID}}">
+  <div class="d-flex align-items-start mb-2">
+    {{template "breadcrumb" .Breadcrumb}}
+    <div class="ms-auto d-flex gap-2 admin-only">
+      <button class="btn btn-sm btn-outline-secondary" data-action="new-subfolder" data-id="{{.Folder.ID}}"><i class="bi bi-folder-plus"></i> Subfolder</button>
+      <button class="btn btn-sm btn-outline-secondary" data-action="rename-folder" data-id="{{.Folder.ID}}" data-name="{{.Folder.Name}}" data-description="{{.Folder.Description}}" data-icon="{{.Folder.Icon}}" data-sort-order="{{.Folder.SortOrder}}"><i class="bi bi-pencil"></i> Rename</button>
+      <button class="btn btn-sm btn-outline-danger" data-action="delete-folder" data-id="{{.Folder.ID}}"><i class="bi bi-trash"></i> Delete</button>
+    </div>
+  </div>
+
+  <h4 class="mb-1"><i class="bi {{iconOr .Folder.Icon "bi-folder-fill"}} text-warning-emphasis me-1"></i>{{.Folder.Name}}</h4>
+  {{if .Folder.Description}}<p class="text-body-secondary">{{.Folder.Description}}</p>{{end}}
+
+  {{if .Subfolders}}
+  <h6 class="mt-3 mb-2">Subfolders</h6>
+  <div class="list-group mb-3">
+    {{range .Subfolders}}
+    <a href="#" class="list-group-item list-group-item-action folder-link d-flex align-items-center" data-id="{{.ID}}">
+      <i class="bi {{iconOr .Icon "bi-folder-fill"}} text-warning-emphasis me-2"></i>
+      {{.Name}}
+      <span class="ms-auto text-body-secondary small">{{.FolderCount}} folder(s), {{.AssetCount}} asset(s)</span>
+    </a>
+    {{end}}
+  </div>
+  {{end}}
+
+  <div class="d-flex align-items-center flex-wrap gap-2 mt-3 mb-2">
+    <h6 class="mb-0 me-2">Assets</h6>
+    <form class="d-flex gap-2 flex-wrap align-items-center panel-filter-form" data-folder-id="{{.Folder.ID}}">
+      <select class="form-select form-select-sm" name="item_type_id" style="width:auto">
+        <option value="">All Types</option>
+        {{range .ItemTypes}}<option value="{{.ID}}" {{if eq .ID $.FilterType}}selected{{end}}>{{.Name}}</option>{{end}}
+      </select>
+      <select class="form-select form-select-sm" name="status_id" style="width:auto">
+        <option value="">All Statuses</option>
+        {{range .Statuses}}<option value="{{.ID}}" {{if eq .ID $.FilterStat}}selected{{end}}>{{.Name}}</option>{{end}}
+      </select>
+      <input type="search" class="form-control form-control-sm" name="q" value="{{.Query}}" placeholder="Filter assets&hellip;" style="width:160px">
+    </form>
+    <div class="ms-auto d-flex gap-2">
+      <a class="btn btn-sm btn-outline-secondary" href="/export/assets.csv?folder_id={{.Folder.ID}}&recursive=1"><i class="bi bi-download"></i> Export</a>
+      <button class="btn btn-sm btn-primary admin-only" data-action="new-asset" data-folder-id="{{.Folder.ID}}"><i class="bi bi-plus-lg"></i> Add Asset</button>
+    </div>
+  </div>
+
+  {{if .Assets}}
+  <div class="table-responsive">
+    <table class="table table-sm table-hover asset-table">
+      <thead><tr><th>Asset ID</th><th>Name</th><th>Type</th><th>Status</th><th>Assigned</th></tr></thead>
+      <tbody>
+        {{range .Assets}}
+        <tr class="asset-row" data-id="{{.ID}}">
+          <td>{{.AssetTag}}</td>
+          <td><i class="bi {{iconOr .ItemTypeIcon "bi-box-seam"}} me-1"></i>{{.Name}}</td>
+          <td>{{.ItemTypeName}}</td>
+          <td><span class="badge text-bg-{{.StatusColor}}">{{.StatusName}}</span></td>
+          <td>{{if .AssignedUsername}}{{.AssignedUsername}}{{else}}<span class="text-body-secondary">&mdash;</span>{{end}}</td>
+        </tr>
+        {{end}}
+      </tbody>
+    </table>
+  </div>
+  {{$pages := ceilDiv .Total .PageSize}}
+  {{if gt $pages 1}}
+  <nav>
+    <ul class="pagination pagination-sm">
+      {{range $i := seqFrom1 $pages}}
+      <li class="page-item {{if eq $i $.Page}}active{{end}}">
+        <a class="page-link panel-page-link" href="#" data-folder-id="{{$.Folder.ID}}" data-page="{{$i}}">{{$i}}</a>
+      </li>
+      {{end}}
+    </ul>
+  </nav>
+  {{end}}
+  {{else}}
+  <p class="text-body-secondary">No assets in this folder yet.</p>
+  {{end}}
+</div>
+{{end}}