docs: add routing page (#9550)

- Add a new homepage to `book` project for the routing page
- Move all main doc pages to be under `/v2/learn` (and added redirects + fixed links across docs)
- Other: add admin components to resources dropdown + fixes to search on mobile.

Closes DX-955

Preview: https://docs-v2-git-docs-router-page-medusajs.vercel.app/v2

www/apps/resources/app/recipes/b2b/page.mdx

@@ -173,13 +173,13 @@ You can create a B2B module that adds necessary data models to represent a B2B c
 
 <CardList items={[
   {
-    href: "!docs!/basics/modules",
+    href: "!docs!/learn/basics/modules",
     title: "Create Module",
     text: "Learn how to create a module in Medusa.",
     icon: AcademicCapSolid,
   },
   {
-    href: "!docs!/basics/modules#1-create-data-model",
+    href: "!docs!/learn/basics/modules#1-create-data-model",
     title: "Create Data Models",
     text: "Learn how to create data models.",
     icon: AcademicCapSolid,
@@ -187,7 +187,7 @@ You can create a B2B module that adds necessary data models to represent a B2B c
 ]} />
 
 {/* <Card
-  href="!docs!/advanced-development/modules/module-relationships"
+  href="!docs!/learn/advanced-development/modules/module-relationships"
   title="Create Module Relationships"
   text="Learn how to create a relationship between modules."
   icon={AcademicCapSolid}
@@ -573,7 +573,7 @@ To implement a more advanced B2B sales flow, add custom data models such as `Com
 This provides more granular control of your B2B sales and allows you to build features like privileges, limits, and more. 
 
 <Card
-  href="!docs!/basics/modules#1-create-data-model"
+  href="!docs!/learn/basics/modules#1-create-data-model"
   title="Create a Data Model"
   text="Learn how to create a custom data model in a module."
   icon={AcademicCapSolid}
@@ -588,7 +588,7 @@ On the frontend clients communicating with your store, such as the storefront, y
 The API route can check if the customer has any group with an associated company.
 
 <Card
-  href="!docs!/basics/api-routes"
+  href="!docs!/learn/basics/api-routes"
   title="Create an API Route"
   text="Learn how to create an API Route in Medusa."
   icon={AcademicCapSolid}
@@ -724,19 +724,19 @@ The Medusa Admin plugin can be extended to add widgets, new pages, and setting p
 
 <CardList items={[
   {
-    href: "!docs!/advanced-development/admin/widgets",
+    href: "!docs!/learn/advanced-development/admin/widgets",
     title: "Create Admin Widget",
     text: "Learn how to add widgets into existing admin pages.",
     icon: AcademicCapSolid,
   },
   {
-    href: "!docs!/advanced-development/admin/ui-routes",
+    href: "!docs!/learn/advanced-development/admin/ui-routes",
     title: "Create Admin UI Routes",
     text: "Learn how to add new pages to your Medusa Admin.",
     icon: AcademicCapSolid,
   },
   {
-    href: "!docs!/advanced-development/admin/setting-pages",
+    href: "!docs!/learn/advanced-development/admin/setting-pages",
     title: "Create Admin Setting Page",
     text: "Learn how to add new page to the Medusa Admin settings.",
     icon: AcademicCapSolid,