Add iOS CI and polish project documentation

[epinethrone]

What changed

• Adds an iOS Simulator build workflow for pushes to main, pull requests, and manual runs.
• Adds a separate Xcode static-analysis workflow for pull requests, weekly health checks, and manual runs.
• Uses least-privilege repository permissions, concurrency cancellation, timeouts, a safe CI configuration stub, and a commit-pinned official checkout action.
• Adds monthly Dependabot maintenance for GitHub Actions.
• Rewrites the README around CasaGlow's native SwiftUI experience, smart home management capabilities, visual automation editor, architecture, setup, and direct Home Assistant integration.
• Updates the public repository description and topics for stronger Home Assistant, smart home, SwiftUI, iOS, Apple Home, and home automation discoverability.

Why

CasaGlow previously had no repository CI and its README understated the scope of the app. The generic Swift Package workflow suggested by GitHub does not apply because CasaGlow is an Xcode iOS application. These workflows validate the actual project while the new README gives potential users and contributors a clear, accurate entry point.

Validation

• Full local xcodebuild analyze succeeds for a generic iOS Simulator destination.
• All workflow and Dependabot YAML files parse successfully.
• git diff --check passes.
• The remaining compiler warnings predate this documentation and CI change.