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/asset_fields.html

@@ -0,0 +1,34 @@
+{{define "asset_fields_only"}}
+{{if .}}
+<h6 class="mt-3 mb-2">Type-Specific Fields</h6>
+{{range .}}
+{{$fv := .}}
+<div class="mb-2">
+  <label class="form-label" for="field-{{.Def.ID}}">{{.Def.Name}}{{if .Def.Required}} <span class="text-danger">*</span>{{end}}</label>
+  {{if eq .Def.FieldType "long_text"}}
+  <textarea class="form-control" id="field-{{.Def.ID}}" name="field_{{.Def.ID}}" rows="3" {{if .Def.Required}}required{{end}}>{{.Value}}</textarea>
+  {{else if eq .Def.FieldType "boolean"}}
+  <select class="form-select" id="field-{{.Def.ID}}" name="field_{{.Def.ID}}">
+    <option value="false" {{if ne .Value "true"}}selected{{end}}>No</option>
+    <option value="true" {{if eq .Value "true"}}selected{{end}}>Yes</option>
+  </select>
+  {{else if eq .Def.FieldType "dropdown"}}
+  <select class="form-select" id="field-{{.Def.ID}}" name="field_{{.Def.ID}}" {{if .Def.Required}}required{{end}}>
+    <option value="">&mdash;</option>
+    {{range .Def.Options}}<option value="{{.}}" {{if eq . $fv.Value}}selected{{end}}>{{.}}</option>{{end}}
+  </select>
+  {{else if eq .Def.FieldType "date"}}
+  <input type="date" class="form-control" id="field-{{.Def.ID}}" name="field_{{.Def.ID}}" value="{{.Value}}" {{if .Def.Required}}required{{end}}>
+  {{else if eq .Def.FieldType "number"}}
+  <input type="number" step="any" class="form-control" id="field-{{.Def.ID}}" name="field_{{.Def.ID}}" value="{{.Value}}" {{if .Def.Required}}required{{end}}>
+  {{else if eq .Def.FieldType "url"}}
+  <input type="url" class="form-control" id="field-{{.Def.ID}}" name="field_{{.Def.ID}}" value="{{.Value}}" {{if .Def.Required}}required{{end}}>
+  {{else if eq .Def.FieldType "ip_address"}}
+  <input type="text" pattern="^[0-9a-fA-F:\.]+$" class="form-control" id="field-{{.Def.ID}}" name="field_{{.Def.ID}}" value="{{.Value}}" placeholder="192.168.1.1" {{if .Def.Required}}required{{end}}>
+  {{else}}
+  <input type="text" class="form-control" id="field-{{.Def.ID}}" name="field_{{.Def.ID}}" value="{{.Value}}" {{if .Def.Required}}required{{end}}>
+  {{end}}
+</div>
+{{end}}
+{{end}}
+{{end}}