docs: Clean up documentation assets and update index

Index Documentation Updates:
- Updated index.rst with latest content structure
- Improved navigation and organization

Asset Cleanup:
- Removed outdated PDF documentation files:
  - DualMCU_R-ONE_V2.pdf (legacy documentation)
  - dualmcuone.pdf (superseded by current docs)
  - esp32-c6_datasheet_en.pdf (not relevant for ESP32-H2)

These changes streamline the documentation structure and remove obsolete files that could cause confusion for ESP32-H2 development.

Author: GitHub Actions

software/sphinx/src/source/_static/DualMCU_R-ONE_V2.pdf

@@ -22,7 +22,7 @@ Documentation for the UNIT PULSAR H2 Development Board. This board is a versatil
 .. raw:: html
 
    <div style="text-align: center;">
-      <button style="background-color: #77dd77; color: white; border: none; padding: 10px 20px; margin-right: 10px;" onclick="window.open('./_static/dualmcuone.pdf', '_blank')">Download PDF version</button>
+      <a href="https://unit-electronics-mx.github.io/unit_pulsar_esp32_h2/unit_pulsar_esp32_h2_sphinx.pdf" target="_blank" rel="noopener noreferrer" role="button" style="background-color: #77dd77; color: white; border: none; padding: 10px 20px; margin-right: 10px; text-decoration: none; display: inline-block;">Download PDF version</a>
    </div>