docs: modernize README (#26458)

* docs: modernize README with hero logo, vehicle icons, and fixed links

Add PX4 and Dronecode SVG logos to the repo, replace broken external
Dronecode logo URL, fix SITL badge branch from master to main, and
restructure the README with centered branding, airframe icon row,
quick-start section, and consolidated documentation links.

docs/index.md

@@ -4,9 +4,9 @@ layout: home
 
 hero:
   name: "PX4"
-  text: "User Guide"
-  tagline: PX4 is the Open Source Autopilot for Professional Drone Developers.
-  image: /logo_pro_small.png
+  text: "Autopilot"
+  tagline: Open-source flight stack for drones and autonomous vehicles. BSD-3 licensed. Vendor neutral.
+  image: /px4-logo.svg
   actions:
     - theme: brand
       text: Read the docs
@@ -20,22 +20,21 @@ hero:
 
 features:
   - title: Modular Architecture
-    details: PX4 is highly modular and extensible both in terms of hardware and software. It utilizes a port-based architecture - which means when developers add components, the extended system does not lose robustness or performance.
-  - title: Open Source
-    details: PX4 is co-developed with a global development community. The flightstack is not just fulfilling the needs of one lab or one company, but has been intended as a general toolkit and is widely used and adopted in the industry.
-  - title: Configurability
-    details: PX4 offers optimised APIs and SDKs for developers working with integrations. All the modules are self-contained and can be easily exchanged against a different module without modifying the core. Features are easy to deploy and reconfigure.
-  - title: Autonomy Stack
-    details: PX4 is designed to be deeply coupled with embedded computer vision for autonomous capabilities . The framework lowers the barrier of entry for developers working on localization and obstacle detection algorithms.
-  - title: Real-world Validation
-    details: Thousands of commercial PX4 based systems have been deployed worldwide. In parallel, dedicated flight test team clocking up thousands of flight hours each month running hardware and software tests to ensure the codebase's safety and reliability.
+    details: Built on uORB, a DDS-compatible publish/subscribe middleware. Every module runs as its own thread, fully parallelized and thread safe. Build custom configurations and strip out what you don't need.
+  - title: Wide Hardware Support
+    details: Supports Pixhawk-standard flight controllers and a growing range of boards beyond that standard. DroneCAN peripherals run PX4 firmware in CAN node mode. No vendor lock-in.
+  - title: Developer Friendly
+    details: First-class MAVLink and DDS/ROS 2 integration. Comprehensive SITL simulation, hardware-in-the-loop testing, and log analysis tools. MAVSDK provides a high-level SDK/API for programmatic vehicle interaction.
+  - title: Autonomy Ready
+    details: Extensible architecture for advanced autonomy. External modes, offboard control, and DDS/ROS 2 interfaces provide the building blocks for computer vision, GPS-denied navigation, and custom flight behaviors.
+  - title: Proven at Scale
+    details: Millions of vehicles deployed worldwide across commercial, defense, and research applications. Continuous flight testing validates the codebase across multirotors, fixed-wing, VTOL, helicopters, rovers, and more.
   - title: Permissive License
-    details: PX4 is free to use and modify under the terms of the permissive BSD 3-clause license. Which means the software also allows proprietary use and allows the releases under the license to be incorporated into proprietary products.
+    details: BSD 3-Clause. Use it, modify it, ship it in proprietary products. You only need to include the original copyright notice and license text.
   - title: Interoperability
-    details: Beyond being a robust flight stack, PX4 offers an ecosystem of supported devices. The project also leads the standardarization effort for the advancement of communications, peripherals integration, and power management solutions.
-
-  - title: Powerful Safety Features
-    details: Great safety features including automated failsafe behaviour, support for different return modes, parachutes etc. are by default already included in the codebase. The features are easily configurable and tunable for custom systems.
+    details: Part of a modular ecosystem. PX4 (autopilot), MAVLink (protocol), QGroundControl (ground station), Pixhawk (hardware standard), MAVSDK (SDK/API), and ROS 2 via DDS or Zenoh. All Dronecode projects, all open source.
+  - title: Vendor Neutral Governance
+    details: Hosted by the Dronecode Foundation under the Linux Foundation. No single company owns the name or controls the roadmap. Community-driven with a weekly open dev call.
 
 search: false
 footer: BSD 3-clause license