Restructure repository for multiple integrations

- Moved Strike integration to integrations/strike/
- Created main README.md with repository overview
- Updated URLs to Gitea repository (git.martien.io)
- Removed old root-level custom_components directory
- Set up structure to support multiple future integrations

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

integrations/strike/hacs.json

@@ -0,0 +1,7 @@
+{
+  "name": "Strike Bitcoin Sensor",
+  "content_in_root": false,
+  "filename": "strike",
+  "render_readme": true,
+  "homeassistant": "2023.1.0"
+}