Add Chennai FOSS 2026 HTML slide deck for DevOps-OS talk

[Copilot]

This pull request adds a new section to the documentation for sharing and viewing DevOps-OS conference presentations, with a focus on the "Chennai FOSS 2026" talk. It introduces a dedicated "Talks & Presentations" section, provides a GitHub Pages-friendly presentation deck, and includes an embedded playback experience for easy access during events.

New documentation section for talks and presentations:

• Added a "Talks & Presentations" section to the documentation sidebar and index, giving users a central place to find conference-ready DevOps-OS decks. [1] [2]

Chennai FOSS 2026 presentation resources:

• Created a dedicated page for the "Chennai FOSS 2026" presentation with options to open the deck in a new tab or view it embedded directly from the documentation, including presenter notes for usage guidance.
• Added a reference to the "Chennai FOSS 2026 Presentation" in the main documentation index for discoverability.
• Listed the "Chennai FOSS 2026" talk in the new "Talks & Presentations" section with a brief description and direct link.- [x] Review the existing GitHub Pages/Hugo documentation structure and confirm where the presentation can be published

• Install the Python test dependencies and rerun the existing pytest suite for a clean baseline in this session
• Add the Chennai FOSS presentation HTML deck to the Hugo Pages output so it can be served from GitHub Pages
• Add an easy-to-access GitHub Pages documentation entry that links to and embeds the presentation for live session use
• Validate the updated repository state with the existing pytest suite and a Hugo site build or local preview relevant to the pages changes