feat: Material You colors, settings backup/restore, add LICENSE

- Material You toggle: bars/rings use wallpaper-derived system accents on
  Android 12+ (ThemeColors.sessionFill/weeklyFill), Claude brand colors otherwise
- Settings backup/restore via SAF (export/import JSON); session cookie never
  included so backups are safe to store anywhere
- Add source-available LICENSE (mirrors SyncFlow's), with Anthropic trademark note

Built + installed on emulator, launches clean.

LICENSE

@@ -0,0 +1,45 @@
+Claude Usage Widget Source-Available License
+Copyright (c) 2026 Amir Khodak. All rights reserved.
+
+This is NOT an OSI-approved open-source license. The source code is made
+publicly viewable ("source-available"), but the rights granted are limited as
+described below. Where this license is silent, all rights are reserved.
+
+1. DEFINITIONS
+   "Software" means the Claude Usage Widget source code, assets, and
+   documentation in this repository. "You" means anyone other than the
+   copyright holder.
+
+2. WHAT YOU MAY DO
+   a. View, read, and study the Software.
+   b. Clone or fork the repository for your own private, personal,
+      non-commercial use and experimentation.
+   c. Build the Software from source and run it on devices you personally own.
+   d. Submit contributions (pull requests) back to this repository; by doing so
+      you license your contribution to the copyright holder under these terms.
+
+3. WHAT YOU MAY NOT DO (without the copyright holder's prior written permission)
+   a. Redistribute, publish, or make available the Software or any derivative
+      work — in source or binary/APK form — to any third party or app store
+      (including but not limited to Google Play, F-Droid, Amazon Appstore,
+      Gitea/GitHub releases, or any website).
+   b. Use the Software, in whole or in part, for any commercial purpose.
+   c. Sell, sublicense, rent, or offer the Software as a service.
+   d. Use the names, app identity ("Claude Usage Widget"), package identifier
+      ("me.khodak.claudeusage"), logos, or signing keys of the original work.
+   e. Remove or alter this license or the copyright notice.
+
+4. RESERVED RIGHTS
+   All publishing and distribution rights are reserved exclusively to the
+   copyright holder. Only the copyright holder may publish official builds.
+
+5. TRADEMARK NOTE
+   "Claude" is a trademark of Anthropic. This is an unofficial, independent
+   utility and is not affiliated with or endorsed by Anthropic.
+
+6. NO WARRANTY
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM,
+   DAMAGES, OR OTHER LIABILITY ARISING FROM THE SOFTWARE OR ITS USE.
+
+To request permission for anything in section 3, contact the copyright holder.