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

flake.lock

@@ -5,11 +5,11 @@
         "nixpkgs-lib": "nixpkgs-lib"
       },
       "locked": {
-        "lastModified": 1778716662,
-        "narHash": "sha256-m1Yf0wZ8j1OHjTc2UwHwyQRSnNeSgLJOd7q5Y45hzi4=",
+        "lastModified": 1782949081,
+        "narHash": "sha256-vp6Y/Grm98ESt6ceOkWiHWyZRDV3J1RID4w+6NWK9yA=",
         "owner": "hercules-ci",
         "repo": "flake-parts",
-        "rev": "f7c1a2d347e4c52d5fb8d10cb4d94b5884e546fb",
+        "rev": "17c9d6cdfc60c64f4ee8d306f9bc0b4ccb51481e",
         "type": "github"
       },
       "original": {
@@ -73,11 +73,11 @@
     },
     "nixpkgs-lib": {
       "locked": {
-        "lastModified": 1777168982,
-        "narHash": "sha256-GOkGPcboWE9BmGCRMLX3worL4EMnsnG8MyKmXNeYuhQ=",
+        "lastModified": 1782614948,
+        "narHash": "sha256-ePjCwr1sNm9NYUqywL7QfK3JnlS015msC+eBu2zKlp8=",
         "owner": "nix-community",
         "repo": "nixpkgs.lib",
-        "rev": "f5901329dade4a6ea039af1433fb087bd9c1fe14",
+        "rev": "db3f255737b94216eb71cce308e2912cf6bc2d7c",
         "type": "github"
       },
       "original": {
@@ -88,11 +88,11 @@
     },
     "nixpkgs_2": {
       "locked": {
-        "lastModified": 1778869304,
-        "narHash": "sha256-30sZNZoA1cqF5JNO9fVX+wgiQYjB7HJqqJ4ztCDeBZE=",
+        "lastModified": 1784497964,
+        "narHash": "sha256-vlHUuqAcbcH2RKmHbPiuQzbv1pnzzavXnI62RD0bqCU=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "d233902339c02a9c334e7e593de68855ad26c4cb",
+        "rev": "241313f4e8e508cb9b13278c2b0fa25b9ca27163",
         "type": "github"
       },
       "original": {