refactor: replace legacy tw-flex utility classes with flex-text-block/inline (#36778)

## Summary

Replace combinations of `tw-flex tw-items-center` (with optional
`tw-gap-*`) with semantic `flex-text-block` or `flex-text-inline`
classes across 15 template files.

This follows the refactoring direction outlined in #35015 ("Refactor
legacy `tw-flex tw-items-center tw-gap-xx` to `flex-text-block` or
`flex-text-inline`").

## Changes

### Replacement rules applied:
- `tw-flex tw-items-center tw-gap-2` → `flex-text-block` (both have
`gap: 0.5rem`)
- `tw-flex tw-items-center tw-gap-1` → `flex-text-inline` (both have
`gap: 0.25rem`)
- `tw-flex tw-items-center` (no explicit gap) → `flex-text-block` where
the element is block-level and children benefit from the default gap
- `tw-flex tw-items-center` (inline context, e.g. `<a>`, `<span>`) →
`flex-text-inline`

### Files modified (15):
- `templates/admin/config.tmpl` — config page dt elements
- `templates/admin/repo/unadopted.tmpl` — unadopted repo list items
- `templates/base/head_navbar.tmpl` — active stopwatch popup
- `templates/org/header.tmpl` — org header action buttons
- `templates/org/home.tmpl` — member/team count links
- `templates/org/settings/labels.tmpl` — labels page header
- `templates/repo/branch/list.tmpl` — branch list header
- `templates/repo/commits_table.tmpl` — commits table header
- `templates/repo/diff/box.tmpl` — diff detail box
- `templates/repo/diff/new_review.tmpl` — review form header
- `templates/repo/issue/card.tmpl` — issue card unpin button
- `templates/repo/issue/view_content/attachments.tmpl` — attachment file
size
- `templates/repo/migrate/migrate.tmpl` — migration service cards
- `templates/shared/user/org_profile_avatar.tmpl` — org profile header
- `templates/webhook/new.tmpl` — webhook type dropdown text

### What was NOT changed:
- Elements with `tw-justify-between` or `tw-justify-center` (these need
additional classes)
- Elements whose children use explicit margins (`tw-mr-*`, `tw-ml-*`)
that would conflict with the gap from flex-text classes
- Fomantic UI form elements with special layout requirements

## Notes
- This PR was created with AI assistance (Claude). All changes were
reviewed individually to ensure semantic correctness and zero unintended
visual changes.
- No functional changes — purely CSS class refactoring.

Closes: part of #35015

Signed-off-by: xiaox315 <xiaox315@users.noreply.github.com>
Co-authored-by: xiaox315 <xiaox315@users.noreply.github.com>

templates/org/header.tmpl

@@ -7,7 +7,7 @@
 				{{if .Org.Visibility.IsLimited}}<span class="ui large basic horizontal label">{{ctx.Locale.Tr "org.settings.visibility.limited_shortname"}}</span>{{end}}
 				{{if .Org.Visibility.IsPrivate}}<span class="ui large basic horizontal label">{{ctx.Locale.Tr "org.settings.visibility.private_shortname"}}</span>{{end}}
 			</span>
-			<span class="tw-flex tw-items-center tw-gap-1 tw-ml-auto tw-text-16 tw-whitespace-nowrap">
+			<span class="flex-text-inline tw-ml-auto tw-text-16 tw-whitespace-nowrap">
 				{{if .EnableFeed}}
 					<a class="ui basic label button tw-mr-0" href="{{.Org.HomeLink}}.rss" data-tooltip-content="{{ctx.Locale.Tr "rss_feed"}}">
 						{{svg "octicon-rss" 24}}

templates/org/home.tmpl

@@ -49,7 +49,7 @@
 				{{if .NumMembers}}
 					<h4 class="ui top attached header tw-flex">
 						<strong class="tw-flex-1">{{ctx.Locale.Tr "org.members"}}</strong>
-						<a class="tw-text-text-light tw-flex tw-items-center" href="{{.OrgLink}}/members"><span>{{.NumMembers}}</span> {{svg "octicon-chevron-right"}}</a>
+						<a class="tw-text-text-light flex-text-inline" href="{{.OrgLink}}/members"><span>{{.NumMembers}}</span> {{svg "octicon-chevron-right"}}</a>
 					</h4>
 					<div class="ui attached segment members">
 						{{$isMember := .IsOrganizationMember}}
@@ -63,7 +63,7 @@
 				{{if .IsOrganizationMember}}
 					<div class="ui top attached header tw-flex">
 						<strong class="tw-flex-1">{{ctx.Locale.Tr "org.teams"}}</strong>
-						<a class="tw-text-text-light tw-flex tw-items-center" href="{{.OrgLink}}/teams"><span>{{.Org.NumTeams}}</span> {{svg "octicon-chevron-right"}}</a>
+						<a class="tw-text-text-light flex-text-inline" href="{{.OrgLink}}/teams"><span>{{.Org.NumTeams}}</span> {{svg "octicon-chevron-right"}}</a>
 					</div>
 					<div class="ui attached table segment teams">
 						{{range .Teams}}

templates/org/settings/labels.tmpl

@@ -1,6 +1,6 @@
 {{template "org/settings/layout_head" (dict "ctxData" . "pageClass" "organization settings labels")}}
 <div class="org-setting-content">
-	<div class="tw-flex tw-items-center">
+	<div class="flex-text-block">
 		<div class="tw-flex-1">
 			{{ctx.Locale.Tr "org.settings.labels_desc"}}
 		</div>