[DOCS] Overhaul new-user onboarding, home page, and upload flow (#2347)

Getting started:
- New 15-minute Getting Started guide featuring the two most popular
  tracks (BLE on esp32dev-ble, RF on lilygo-rtl_433), with broker setup
  and a verification step
- Sidebar restructured around the new-user journey; upload options
  numbered by ease; Gitpod upload method removed

Home page:
- VitePress hero with clear actions, larger hero image
- How-it-works pipeline diagram shared as a component (responsive via
  container queries), use-case grid, bigger video tiles without the
  image lightbox, refreshed press coverage list, functions pills
- Support section pointing to Theengs Bridge and
  github.com/sponsors/1technophile

Upload flow:
- Decision-oriented upload landing page (journey strip, method cards,
  comparison table)
- Pre-flight checklist and driver troubleshooting on the web installer
- Guided environment picker (bridge + hardware wizard) replacing the
  filter chips, with manifest-verified recommendations
- Post-flash next-steps card linking to the portal and verification

Board images:
- custom_img key in environments.ini and board photos for all
  web-flashable environments (licenses recorded); private prod_env.ini
  environments excluded from boards-info.json

Corrections:
- RF frequency coverage stated as 433/315/868/915MHz
- Removed references to the retired compatible.openmqttgateway.com
  site (BLE list is decoder.theengs.io), the discontinued Theengs
  Plug, and the private sponsor forum


Claude-Session: https://claude.ai/code/session_01TYysQW8tpmt1dWWuzKhTLi

Co-authored-by: Florian <1technophile@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

docs/participate/support.md

@@ -11,12 +11,12 @@ If you like the project, you can help in different ways. Choose what fits you be
 - Improve docs or examples if you spot unclear steps.
 
 ## Financial support
-- Purchase the [Theengs mobile application](https://app.theengs.io) or the [Theengs plug](https://shop.theengs.io).
+- Purchase the [Theengs mobile application](https://app.theengs.io) or the [Theengs Bridge](https://shop.theengs.io).
 - Sponsor the project [developers](https://github.com/1technophile/OpenMQTTGateway/graphs/contributors).
 - Make a video or blog article about what you built with [OpenMQTTGateway](https://docs.openmqttgateway.com) and share it.
 
-Support open-source development through sponsorship and gain exclusive access to our private forum. Your questions, issues, and feature requests receive priority attention, plus you'll see the roadmap early.
+Support open-source development through sponsorship, it helps keep the project healthy and evolving.
 
 <div style="text-align: center;">
-    <iframe src="https://github.com/sponsors/theengs/button" title="Sponsor Theengs" height="32" width="228" style="border: 0; border-radius: 6px;"></iframe>
+    <iframe src="https://github.com/sponsors/1technophile/button" title="Sponsor 1technophile" height="32" width="228" style="border: 0; border-radius: 6px;"></iframe>
 </div>