create proprietary directory (#2112)

## Description:

Assets in the proprietary directory are copyrighted by OpenFront.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

evan

proprietary/LICENSE

@@ -0,0 +1,43 @@
+Copyright (c) 2025 OpenFront LLC and Contributors
+All Rights Reserved.
+
+PROPRIETARY ASSET LICENSE
+
+The assets in this directory are proprietary and protected by copyright.
+Copyright holders retain their individual copyrights.
+
+PERMITTED USE:
+- You may use these assets for development, testing, and contribution purposes to OpenFront
+- You may use these assets solely as part of the complete OpenFront software package
+- You may view and study these assets for personal educational purposes
+- You may run, compile, and test the software containing these assets
+
+RESTRICTIONS:
+You may NOT:
+- Extract, copy, or use these assets in any other project or work
+- Modify, alter, or create derivative works of these assets for redistribution
+- Redistribute, sublicense, sell, or transfer these assets separately from OpenFront
+- Use these assets for any commercial purpose outside of running OpenFront
+- Remove or alter any copyright notices or this license
+
+CONTRIBUTIONS:
+By contributing assets to this directory, you:
+- Retain copyright to your original work
+- Grant OpenFront LLC a perpetual, worldwide, non-exclusive, royalty-free license to use,
+  modify, and distribute your contributions as part of OpenFront
+- Agree that your contributions will be distributed under this restrictive license
+- Warrant that you have the right to grant these permissions
+
+ATTRIBUTION:
+Individual asset copyrights are held by their respective creators.
+See CONTRIBUTORS.md for attribution details.
+
+NO WARRANTY:
+THE ASSETS ARE 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
+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 ASSETS OR THE USE OR OTHER DEALINGS IN THE ASSETS.
+
+For questions regarding licensing or commercial use, contact: legal@openfront.io