Docs(python): add Python SDK documentation section

[gpretto]

Summary

• Adds a dedicated Python SDK documentation section to the Docusaurus site alongside the existing Java and JavaScript sections
• Introduces 15 feature pages across four module groups (Agent Modules, Connectivity & Identity, Core Modules, RBS Services), each with real code snippets from the cloud-sdk-python repository and a link to the full user guide
• Adds overview, getting started, release notes, support, and troubleshooting pages
• Adds the Python SDK to the homepage feature table and logo assets
• Adds a structured architecture diagram (python-sdk-overview.svg) matching the Java SDK reference style

Pages added

Group	Pages
Agent Modules	Agent Decorators, Agent Gateway, Agent Memory, SAP AI Core
Connectivity & Identity	Destination Service, Identity (IAS), Secret Resolver
Core Modules	Audit Logging, Telemetry & Observability, Object Storage, Runtime Context
RBS Services	DMS, ADMS, Output Management, Print Service

Notes

• Code snippets were verified against the real module APIs in SAP/cloud-sdk-python
• Each feature page links to the corresponding user-guide.md in the cloud-sdk-python repo for deeper reference
• No sync script — pages are hand-authored (first version; automation can be added later)