fix(ui): add help link to footer, show login logo on signin page

- Help link added to footer right-links (next to API and Licenses)
- Login logo (login-logo.png) now shown on the signin page, not just
  the home page. Hidden via onerror when not uploaded.
- Landing page is set to 'login' so home.tmpl never renders — the
  logo needed to be on signin_inner.tmpl instead.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

templates/base/footer_content.tmpl

@@ -36,6 +36,7 @@
 		</div>
 		<a href="{{AssetUrlPrefix}}/licenses.txt">{{ctx.Locale.Tr "licenses"}}</a>
 		{{if .EnableSwagger}}<a href="{{AppSubUrl}}/api/swagger">API</a>{{end}}
+		<a href="{{HelpURL}}" target="_blank">{{ctx.Locale.Tr "help"}}</a>
 		{{template "custom/extra_links_footer" .}}
 	</div>
 </footer>

templates/user/auth/signin_inner.tmpl

@@ -1,4 +1,7 @@
 <div class="ui container fluid">
+	<div class="tw-text-center tw-mb-4">
+		<img src="{{AssetUrlPrefix}}/img/login-logo.png" style="max-width: 220px; max-height: 80px; object-fit: contain;" onerror="this.style.display='none'">
+	</div>
 	{{if or (not .LinkAccountMode) (and .LinkAccountMode .LinkAccountModeSignIn)}}
 	{{template "base/alert" .}}
 	{{end}}