OAuth Support (#53)

Rips out the old auth method, adds OAuth support. Fixes #51.

Tested Platforms:
- [x] Linux
    - [x] Flatpak
    - [x] Native (Nix)
- [x] Android
- [ ] Windows
- [ ] MacOS

Reviewed-on: Nexus/nexus#53

.github/workflows/flatpak.yml

@@ -34,4 +34,4 @@ jobs:
         uses: actions/upload-artifact@v6
         with:
           name: flatpak-${{ matrix.arch }}
-          path: result/nexus.federated.Nexus.flatpak
+          path: result/nexus.federated.nexus.flatpak

.github/workflows/windows.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Set up Flutter
         uses: subosito/flutter-action@v2
         with:
-          flutter-version: 3.41.9
+          flutter-version: 3.44.4
 
       - name: Set up Go
         uses: actions/setup-go@v6
@@ -52,12 +52,6 @@ jobs:
           cp /mingw64/bin/libwinpthread-1.dll build/windows/x64/runner/Release/
           cp /mingw64/bin/libstdc++-6.dll build/windows/x64/runner/Release/
 
-      - name: Upload exe zip
-        uses: actions/upload-artifact@v6
-        with:
-          name: windows-portable
-          path: build/windows/x64/runner/Release/
-
       - name: Install Inno Setup
         run: choco install innosetup -y