feat(backend): init aris-backend with Hono

- Add apps/aris-backend package with Hono server
- Add /health endpoint
- Add backend-spec.md with design decisions

Co-authored-by: Ona <no-reply@ona.com>

apps/aris-backend/package.json

@@ -0,0 +1,19 @@
+{
+	"name": "@aris/backend",
+	"version": "0.0.0",
+	"type": "module",
+	"main": "src/index.ts",
+	"scripts": {
+		"dev": "bun run --watch src/index.ts",
+		"start": "bun run src/index.ts",
+		"test": "bun test src/"
+	},
+	"dependencies": {
+		"@aris/core": "workspace:*",
+		"@aris/source-location": "workspace:*",
+		"@aris/source-weatherkit": "workspace:*",
+		"better-auth": "^1",
+		"hono": "^4",
+		"postgres": "^3"
+	}
+}