Prepare for public distribution v1.0.0

- Remove all personal data from source code (HA IP, JWT tokens)
- Move secrets to .env configuration (gitignored)
- Create .env.example template for new installations
- Add centralized env() helper, eliminate code duplication (~120 lines removed)
- Add input validation on inventory operations (quantity bounds, location whitelist)
- Remove sensitive credential exposure in API responses
- Remove database and runtime files from Git tracking
- Disable database push-to-GitHub backup (local-only backup now)
- Update .gitignore for distribution
- Add comprehensive README with installation guide
- Add CHANGELOG.md for version tracking
- Add MIT LICENSE
- Add author/license headers to all source files
- TTS defaults now empty (configured per-installation via .env)

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Stimpfl Daniel
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.