feat(oauth-gateway): implement multi-tenant OAuth gateway service

- Added a new OAuth gateway service to handle multi-tenant authentication callbacks.
- Implemented routing logic for provider callbacks, including tenant slug validation and host resolution.
- Introduced configuration management for environment variables and service settings.
- Created Dockerfile and package.json for service deployment and dependencies.
- Added HTML response for restricted tenant access and updated static web components accordingly.

Signed-off-by: Innei <tukon479@gmail.com>

be/apps/oauth-gateway/package.json

@@ -0,0 +1,24 @@
+{
+  "name": "@afilmory/oauth-gateway",
+  "type": "module",
+  "version": "0.1.0",
+  "private": true,
+  "scripts": {
+    "build": "vite build",
+    "dev": "nodemon",
+    "start": "node dist/main.js"
+  },
+  "dependencies": {
+    "@afilmory/utils": "workspace:*",
+    "@hono/node-server": "^1.13.5",
+    "hono": "^4.6.12",
+    "zod": "catalog:"
+  },
+  "devDependencies": {
+    "@types/node": "^22.10.2",
+    "nodemon": "3.1.10",
+    "typescript": "catalog:",
+    "vite": "7.1.12",
+    "vite-node": "3.2.4"
+  }
+}