docs: Update desktop-app README to reflect Responsively App

[dollaransh17]

Replace Electron React Boilerplate content with proper Responsively App information:

• Update title and description to match the actual project
• Replace boilerplate badges with relevant ones
• Add proper feature list with emojis
• Update installation and development instructions
• Replace boilerplate sections with Responsively App-specific content
• Update links to point to correct repositories and resources
• Remove outdated backers/sponsors sections from boilerplate
• Update license attribution

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