fix: correct TypeScript baseUrl to resolve path aliases during build

Changed baseUrl from "./" to "./src" and updated paths to be relative
to src directory. This allows TypeScript to correctly resolve imports
using @domain/*, @application/*, and @infrastructure/* aliases during
compilation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

apps/backend/tsconfig.json

@@ -9,7 +9,7 @@
     "target": "ES2021",
     "sourceMap": true,
     "outDir": "./dist",
-    "baseUrl": "./",
+    "baseUrl": "./src",
     "incremental": true,
     "skipLibCheck": true,
     "strictNullChecks": true,
@@ -23,9 +23,9 @@
     "resolveJsonModule": true,
     "esModuleInterop": true,
     "paths": {
-      "@domain/*": ["src/domain/*"],
-      "@application/*": ["src/application/*"],
-      "@infrastructure/*": ["src/infrastructure/*"]
+      "@domain/*": ["domain/*"],
+      "@application/*": ["application/*"],
+      "@infrastructure/*": ["infrastructure/*"]
     }
   },
   "include": ["src/**/*"],