refactor: Externalize web UI to index.html

Refactors the embedded web UI in the API server to be loaded from a
separate index.html file instead of a large inline string.

This improves maintainability by separating the presentation layer
(HTML/CSS/JS) from the backend Python logic.

CHANGELOG.md

@@ -4,6 +4,36 @@ All notable changes to this project are documented in this file.
 
 The format is based on Keep a Changelog and this project uses Semantic Versioning.
 
+## [0.1.20] - 2026-03-08
+
+### Changed
+
+- Refactored the embedded web UI in the API server to be loaded from a separate `index.html` file instead of a large inline string, improving maintainability.
+
+## [0.1.19] - 2026-03-08
+
+### Added
+
+- Added `POST /unpair` endpoint and "Unpair Device" button in the web UI to remove a Bluetooth device from the host's paired devices.
+
+## [0.1.18] - 2026-03-08
+
+### Added
+
+- Added `POST /pair` endpoint and "Pair Device" button in the web UI to easily pair/trust the printer via `bluetoothctl` for Classic Bluetooth connections.
+
+## [0.1.17] - 2026-03-08
+
+### Added
+
+- Added automatic fallback to BLE connection if Classic Bluetooth (RFCOMM) fails with `[Errno 12] Out of memory`, a common issue on Linux with stale device states.
+
+## [0.1.16] - 2026-03-08
+
+### Fixed
+
+- Corrected typos in the Code128B bit pattern table for characters '$' (ASCII 36) and ')' (ASCII 41), which caused incorrect barcodes to be generated.
+
 ## [0.1.15] - 2026-03-07
 
 ### Fixed