[Port] gitea#29982 Introduce `.secondary-nav` and handle `.page-content` spacing universally

Fixes: https://github.com/go-gitea/gitea/issues/29981. Introduce
`.secondary-nav` as a universal way for styling and margin adjustments
inside `.page-content`.

If the first child of `.page-content` is `.secondary-nav`, we add margin
below it, otherwise we add padding to the first child. Notable changes:

- `--color-header-wrapper` is replaced with `--color-secondary-nav-bg`.
- `navbar` class is removed.

Co-authored-by: Giteabot <[e-mail]>
Co-authored-by: wxiaoguang <[e-mail]>

---

Conflict resolution: Trivial conflict & changed selector to reflect new
classes.
Ref: https://codeberg.org/forgejo/forgejo/issues/2776
(cherry picked from commit 3ccda41a539b8ba7841919ee12dc2877ddc03818)

templates/admin/layout_head.tmpl

···
 {{template "base/head" .ctxData}}
 <div role="main" aria-label="{{.ctxData.Title}}" class="page-content {{.pageClass}}">
-	<div class="ui container gt-mb-4">
+	<div class="ui container">
 		{{template "base/alert" .ctxData}}
 	</div>
 	<div class="ui container fluid padded flex-container">

templates/explore/navbar.tmpl

···
-<overflow-menu class="ui secondary pointing tabular top attached borderless menu navbar">
+<overflow-menu class="ui secondary pointing tabular top attached borderless menu secondary-nav">
 	<div class="overflow-menu-items tw-justify-center">
 		<a class="{{if .PageIsExploreRepositories}}active {{end}}item" href="{{AppSubUrl}}/explore/repos">
 			{{svg "octicon-repo"}} {{ctx.Locale.Tr "explore.repos"}}

templates/repo/header.tmpl

···
-<div class="header-wrapper">
+<div class="secondary-nav">
 {{with .Repository}}
 	<div class="ui container">
 		<div class="repo-header">
···
 		{{if .IsGenerated}}<div class="fork-flag">{{ctx.Locale.Tr "repo.generated_from"}} <a href="{{(.TemplateRepo ctx).Link}}">{{(.TemplateRepo ctx).FullName}}</a></div>{{end}}
 	</div>
 {{end}}
-	<overflow-menu class="ui container secondary pointing tabular top attached borderless menu navbar tw-pt-0 tw-my-0">
+	<overflow-menu class="ui container secondary pointing tabular top attached borderless menu tw-pt-0 tw-my-0">
 		{{if not (or .Repository.IsBeingCreated .Repository.IsBroken)}}
 			<div class="overflow-menu-items">
 				{{if .Permission.CanRead $.UnitTypeCode}}

templates/user/auth/link_account.tmpl

···
 {{template "base/head" .}}
 <div role="main" aria-label="{{.Title}}" class="page-content user link-account">
-	<overflow-menu class="ui secondary pointing tabular top attached borderless menu navbar tw-bg-header-wrapper">
+	<overflow-menu class="ui secondary pointing tabular top attached borderless menu secondary-nav">
 		<div class="overflow-menu-items tw-justify-center">
 			<!-- TODO handle .ShowRegistrationButton once other login bugs are fixed -->
 			{{if not .AllowOnlyInternalRegistration}}

templates/user/auth/signin_navbar.tmpl

···
 {{if or .EnableOpenIDSignIn .EnableSSPI}}
-<overflow-menu class="ui secondary pointing tabular top attached borderless menu navbar tw-bg-header-wrapper">
+<overflow-menu class="ui secondary pointing tabular top attached borderless menu navbar secondary-nav">
 	<div class="overflow-menu-items tw-justify-center">
 		<a class="{{if .PageIsLogin}}active {{end}}item" rel="nofollow" href="{{AppSubUrl}}/user/login">
 			{{ctx.Locale.Tr "auth.tab_signin"}}

templates/user/auth/signup_openid_navbar.tmpl

···
-<overflow-menu class="ui secondary pointing tabular top attached borderless menu navbar tw-bg-header-wrapper">
+<overflow-menu class="ui secondary pointing tabular top attached borderless menu secondary-nav">
 	<div class="overflow-menu-items tw-justify-center">
 		<a class="{{if .PageIsOpenIDConnect}}active {{end}}item" href="{{AppSubUrl}}/user/openid/connect">
 			{{ctx.Locale.Tr "auth.openid_connect_title"}}

templates/user/dashboard/navbar.tmpl

···
-<div class="dashboard-navbar">
+<div class="secondary-nav tw-border-b tw-border-b-secondary">
 	<div class="ui secondary stackable menu">
 		<div class="item">
 			<div class="ui floating dropdown jump">
···
 	{{end}}
 	</div>
 </div>
-<div class="divider tw-mt-0"></div>

tests/e2e/example.test.e2e.js

···
   await page.click('form button.ui.primary.button:visible');
   // Make sure we routed to the home page. Else login failed.
   await expect(page.url()).toBe(`${workerInfo.project.use.baseURL}/`);
-  await expect(page.locator('.dashboard-navbar span>img.ui.avatar')).toBeVisible();
+  await expect(page.locator('.secondary-nav span>img.ui.avatar')).toBeVisible();
   await expect(page.locator('.ui.positive.message.flash-success')).toHaveText('Account was successfully created. Welcome!');
 
   save_visual(page);

tests/e2e/utils_e2e.js

···
       fullPage: true,
       timeout: 20000,
       mask: [
-        page.locator('.dashboard-navbar span>img.ui.avatar'),
+        page.locator('.secondary-nav span>img.ui.avatar'),
         page.locator('.ui.dropdown.jump.item span>img.ui.avatar'),
       ],
     });

web_src/css/base.css

···
   padding-bottom: 80px;
 }
 
-.page-content.new:is(.repo,.migrate,.org),
-.page-content.profile:is(.user,.organization) {
-  padding-top: 15px;
+/* add margin below .secondary nav when it is the first child */
+.page-content > :first-child.secondary-nav {
+  margin-bottom: 14px;
+}
+
+/* add padding to all content when there is no .secondary.nav. this uses padding instead of
+   margin because with the negative margin on .ui.grid we would have to set margin-top: 0,
+   but that does not work universally for all pages */
+.page-content > :first-child:not(.secondary-nav) {
+  padding-top: 14px;
 }
 
 /* overwrite semantic width of containers inside the main page content div (div with class "page-content") */
···
 }
 
 overflow-menu {
-  margin-bottom: 15px !important;
   border-bottom: 1px solid var(--color-secondary) !important;
   display: flex;
 }
···
 
 overflow-menu .overflow-menu-items .item {
   margin-bottom: 0 !important; /* reset fomantic's margin, because the active menu has special bottom border */
+}
+
+overflow-menu .ui.label {
+  margin-left: 7px !important; /* save some space */
 }
 
 .activity-bar-graph {

web_src/css/dashboard.css

···
   margin: 0 1px; /* Accommodate for Semantic's 1px hacks on .attached elements */
 }
 
-.dashboard .dashboard-navbar {
-  padding: 4px 12px;
+.dashboard .secondary-nav {
+  padding: 1px 12px; /* match .overflow-menu-items in height */
 }
 
-.dashboard .dashboard-navbar .right.menu {
+.dashboard .secondary-nav .right.menu {
   gap: .35714286em;
 }
 
-.dashboard .dashboard-navbar .right.menu div.item {
+.dashboard .secondary-nav .right.menu div.item {
   padding-left: 0.5rem;
 }
 
-.dashboard .dashboard-navbar .org-visibility .label {
+.dashboard .secondary-nav .org-visibility .label {
   margin-left: 5px;
 }
 
-.dashboard .dashboard-navbar .ui.dropdown {
+.dashboard .secondary-nav .ui.dropdown {
   max-width: 100%;
 }

web_src/css/explore.css

···
-.explore .navbar {
-  margin-bottom: 15px !important;
-  background-color: var(--color-header-wrapper) !important;
+.explore .secondary-nav {
   border-width: 1px !important;
 }
 
-.explore .navbar .svg {
+.explore .secondary-nav .svg {
   width: 16px;
   text-align: center;
   margin-right: 5px;

web_src/css/modules/navbar.css

···
   justify-content: center;
   z-index: 1; /* prevent menu button background from overlaying icon */
 }
+
+.secondary-nav {
+  background: var(--color-secondary-nav-bg) !important; /* important because of .ui.secondary.menu */
+}

web_src/css/repo.css

···
   user-select: none;
 }
 
-.repository .navbar {
-  display: flex;
-  justify-content: space-between;
-}
-
-.repository .navbar .ui.label {
-  margin-left: 7px;
-  padding: 3px 5px;
-}
-
 .repository .owner.dropdown {
   min-width: 40% !important;
 }

web_src/css/repo/header.css

···
-.header-wrapper .fork-flag {
+.repository .secondary-nav {
+  padding-top: 12px;
+}
+
+.repository .secondary-nav .fork-flag {
   margin-top: 0.5rem;
   font-size: 12px;
 }
···
 .repo-buttons .ui.labeled.button.disabled > .button {
   pointer-events: none !important;
 }
-
-.repository .header-wrapper {
-  padding-top: 12px;
-  background-color: var(--color-header-wrapper);
-}

web_src/css/themes/theme-gitea-dark.css

···
   --color-input-toggle-background: #2e353b;
   --color-input-border: var(--color-secondary);
   --color-input-border-hover: var(--color-secondary-dark-1);
-  --color-header-wrapper: #181c20;
   --color-light: #00001728;
   --color-light-mimic-enabled: rgba(0, 0, 0, calc(40 / 255 * 222 / 255 / var(--opacity-disabled)));
   --color-light-border: #e8e8ff28;
···
   --color-nav-bg: #16191c;
   --color-nav-hover-bg: var(--color-secondary-light-1);
   --color-nav-text: var(--color-text);
+  --color-secondary-nav-bg: #181c20;
   --color-label-text: var(--color-text);
   --color-label-bg: #73828e4b;
   --color-label-hover-bg: #73828ea0;

web_src/css/themes/theme-gitea-light.css

···
   --color-input-toggle-background: #d0d7de;
   --color-input-border: var(--color-secondary);
   --color-input-border-hover: var(--color-secondary-dark-1);
-  --color-header-wrapper: #f9fafb;
   --color-light: #00001706;
   --color-light-mimic-enabled: rgba(0, 0, 0, calc(6 / 255 * 222 / 255 / var(--opacity-disabled)));
   --color-light-border: #0000171d;
···
   --color-nav-bg: #f6f7fa;
   --color-nav-hover-bg: var(--color-secondary-light-1);
   --color-nav-text: var(--color-text);
+  --color-secondary-nav-bg: #f9fafb;
   --color-label-text: var(--color-text);
   --color-label-bg: #949da64b;
   --color-label-hover-bg: #949da6a0;

web_src/css/user.css

···
   border: 1px solid var(--color-secondary);
 }
 
-#notification_div {
-  padding-top: 15px;
-}
-
 #notification_table {
   background: var(--color-box-body);
   border: 1px solid var(--color-secondary);