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)

.env.example

@@ -0,0 +1,22 @@
+# Dispensa Manager - Configuration
+# Copy this file to .env and fill in your values
+# cp .env.example .env
+
+# Google Gemini AI API Key (required for AI features)
+# Get one at: https://aistudio.google.com/app/apikey
+GEMINI_API_KEY=
+
+# Bring! Shopping List credentials (optional)
+# Sign up at: https://www.getbring.com/
+BRING_EMAIL=
+BRING_PASSWORD=
+
+# TTS (Text-to-Speech) for cooking mode voice guidance (optional)
+# Works with Home Assistant, or any HTTP endpoint that accepts text
+TTS_URL=
+TTS_TOKEN=
+TTS_METHOD=POST
+TTS_AUTH_TYPE=bearer
+TTS_CONTENT_TYPE=application/json
+TTS_PAYLOAD_KEY=message
+TTS_ENABLED=false