docs: move quick starts (#2055)

move quicks starts from deep nesting to main navigation below Home
update reference throughout documentation to absolute URLs

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Move Quick start to main navigation and update related docs to use
absolute /platform links.
> 
> - **Docs navigation**:
> - Move `Quick start` under main navigation by updating `slug` and
`sidebar_position` in `sources/platform/quick-start/index.mdx` and
linking from `sources/platform/actors/development/index.md`.
> - **Link updates**:
> - Replace relative links with absolute `/platform/...` paths across
`actors/development/index.md`, `quick-start/index.mdx`,
`quick-start/start_locally.md`, and `quick-start/start_web_ide.md`
(e.g., `Running Actors`, `Actor` overview, `Deployment`, `Continuous
integration`, `Publishing`).
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
9689e40. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: TC-MO

sources/platform/actors/development/index.md

@@ -12,7 +12,7 @@ slug: /actors/development
 
 This section will guide you through the whole story of [Actor](../index.mdx) development.
 
-You can follow chapters sequentially from [Quick start](./quick_start/index.mdx), where you learn how to create your first Actor in just a few minutes, through the more technical sections describing the whole Actor model, up to the [Performance](/sources/platform/actors/development/performance.md) section, where you learn how to fine-tune your Actor to get the most out of the Apify platform.
+You can follow chapters sequentially from [Quick start](/platform/actors/development/quick-start), where you learn how to create your first Actor in just a few minutes, through the more technical sections describing the whole Actor model, up to the [Performance](/sources/platform/actors/development/performance.md) section, where you learn how to fine-tune your Actor to get the most out of the Apify platform.
 
 import Card from "@site/src/components/Card";
 import CardGrid from "@site/src/components/CardGrid";