removing older videos from home page (#12241)

_Description of what this PR is changing or adding, and why:_ We had
embedded a few older videos on the index page, this PR removes them. We
should probably limit to 2-3 videos on the index page.

_Issues fixed by this PR (if any):_

_PRs or commits this PR depends on (if any):_

## Presubmit checklist

- [ ] If you are unwilling, or unable, to sign the CLA, even for a
_tiny_, one-word PR, please file an issue instead of a PR.
- [ ] If this PR is not meant to land until a future stable release,
mark it as draft with an explanation.
- [ ] This PR follows the [Google Developer Documentation Style
Guidelines](https://developers.google.com/style)—for example, it doesn't
use _i.e._ or _e.g._, and it avoids _I_ and _we_ (first-person
pronouns).
- [ ] This PR uses [semantic line
breaks](https://github.com/dart-lang/site-shared/blob/main/doc/writing-for-dart-and-flutter-websites.md#semantic-line-breaks)
  of 80 characters or fewer.

---------

Co-authored-by: Shams Zakhour (ignore Sfshaza) <[email protected]>

Author: khanhnwin

src/content/data-and-backend/serialization/json.md

@@ -27,6 +27,8 @@ overall process, and "encoding" and "decoding" when specifically
 referring to those processes.
 :::
 
+{% ytEmbed 'ngsxzZt5DoY', 'dart:convert (Technique of the Week)' %}
+
 ## Which JSON serialization method is right for me?
 
 This article covers two general strategies for working with JSON:

src/content/get-started/learn-flutter.md

@@ -26,6 +26,8 @@ in order:
     through some of the most important pieces of 
     building Flutter applications.
 
+{% ytEmbed 'W4JWeQolJsU', 'Build and ship amazing multiplatform iOS and Android apps with one codebase' %}
+
 ## Apply your existing knowledge
 
 * [Flutter for Android developers][]

src/content/index.md

@@ -97,34 +97,10 @@ and [How Flutter makes the most of your platforms][].
 [How to build agentic apps with Flutter and Firebase AI Logic]: {{site.yt.watch}}?v=xo271p-Fl_4
 [How Flutter makes the most of your platforms]: {{site.yt.watch}}?v=flwULzNYRac
 
-## Want to skill up?
+To learn about all of the Flutter video series, see our [videos][] page.
 
-Dive deeper into how Flutter works under the hood!
-Learn [why you write standalone widgets instead of
-using helper methods][standalone-widgets] or
-[what is "BuildContext" and how is it used][buildcontext]?
+We release new videos almost every week!
 
-<div class="card-grid">
-  <div class="card wrapped-card outlined-card">
-    <div class="card-content">
-      {% ytEmbed 'IOyq-eTRhvo', 'Widgets vs helper methods | Decoding Flutter', true %}
-    </div>
-  </div>
-  <div class="card wrapped-card outlined-card">
-    <div class="card-content">
-      {% ytEmbed 'rIaaH87z1-g', 'BuildContext?! | Decoding Flutter', true %}
-    </div>
-  </div>
-</div>
-
-[standalone-widgets]: {{site.yt.watch}}?v=IOyq-eTRhvo
-[buildcontext]: {{site.yt.watch}}?v=rIaaH87z1-g
-
-To learn about all of the Flutter video series,
-see our [videos][] page.
-
-We release new videos almost every week on the Flutter YouTube channel:
-
-<a class="filled-button" target="_blank" href="https://www.youtube.com/@flutterdev">Explore more Flutter videos</a>
+<a class="filled-button" target="_blank" href="https://www.youtube.com/@flutterdev">Check out the Flutter YouTube channel</a>
 
 [videos]: /resources/videos

src/content/perf/best-practices.md

@@ -106,6 +106,18 @@ For more information, check out:
 
 ---
 
+### Use StringBuffer for efficient string building
+
+When you need to build a string from multiple parts, especially inside a loop, 
+using the `+` operator can be inefficient because it creates a new `String` 
+object on each concatenation. A better approach is to use `StringBuffer`, 
+which collects all the strings and concatenates them only once, when you call 
+`toString()`.
+
+{% ytEmbed 'xSsFtDY-nOw', 'StringBuffer (Technique of the Week)' %}
+
+---
+
 ### Use saveLayer() thoughtfully
 
 Some Flutter code uses `saveLayer()`, an expensive operation,

src/content/release/whats-new.md

@@ -18,6 +18,8 @@ join the [flutter-announce][] Google group.
 For Dart, you can join the [Dart Announce][] Google group,
 and review the [Dart changelog][].
 
+{% ytEmbed 'v6Rzo5khNE8', 'What\'s new in Flutter' %}
+
 [Dart Announce]: {{site.groups}}/a/dartlang.org/g/announce
 [Dart changelog]: {{site.github}}/dart-lang/sdk/blob/main/CHANGELOG.md
 [flutter-announce]: {{site.groups}}/forum/#!forum/flutter-announce

src/content/ui/design/cupertino/index.md

@@ -15,6 +15,37 @@ glimpse of the Cupertino package:
 
 {% ytEmbed '3PdUaidHc-E', 'Flutter\'s Cupertino Package' %}
 
+To see some Cupertino widgets in action, the following videos from the
+Widget of the Week series cover a few of them.
+
+<div class="card-grid">
+  <div class="card wrapped-card outlined-card">
+    <div class="card-content">
+      {% ytEmbed 'D0xwcz2IqAY', 'CupertinoRadio (Widget of the Week)' %}
+    </div>
+  </div>
+  <div class="card wrapped-card outlined-card">
+    <div class="card-content">
+      {% ytEmbed '5H-WvH5O29I', 'CupertinoSheetRoute (Widget of the Week)' %}
+    </div>
+  </div>
+  <div class="card wrapped-card outlined-card">
+    <div class="card-content">
+      {% ytEmbed 'esnBf6V4C34', 'CupertinoSlidingSegmentedControl (Widget of the Week)' %}
+    </div>
+  </div>
+  <div class="card wrapped-card outlined-card">
+    <div class="card-content">
+      {% ytEmbed 'ua54JU7k1Us', 'CupertinoCheckbox (Widget of the Week)' %}
+    </div>
+  </div>
+  <div class="card wrapped-card outlined-card">
+    <div class="card-content">
+      {% ytEmbed '24tg_N4sdMQ', 'CupertinoSwitch (Widget of the Week)' %}
+    </div>
+  </div>
+</div>
+
 ## More information {:.no_toc}
 
 To learn more about using the Cupertino

src/content/ui/widgets/cupertino.md

@@ -6,4 +6,6 @@ description: >
   Apple's Human Interface Guidelines for iOS and macOS.
 ---
 
+{{< youtube D0xwcz2IqAY >}}
+
 {% render docs/catalog-page.md, categoryName:"Cupertino", catalog:catalog %}