feat: add datVerifier and tests

- Añade `datVerifier` con `parseDat` y `verifyHashesAgainstDat`
- Añade tests y fixture XML para validar matching por CRC/MD5/SHA1/size
- Añade `fast-xml-parser` en `backend/package.json` (devDependency)

yarn.lock

@@ -1992,6 +1992,17 @@ __metadata:
   languageName: node
   linkType: hard
 
+"fast-xml-parser@npm:^5.3.5":
+  version: 5.3.5
+  resolution: "fast-xml-parser@npm:5.3.5"
+  dependencies:
+    strnum: "npm:^2.1.2"
+  bin:
+    fxparser: src/cli/cli.js
+  checksum: 10c0/ac6232de821c8292436c53a58fc583f073cc5a73d14310b956391512e325e1ef65b950a1d41f5f2715b0d4d363fac2e483d7df1748b344647ea7c7f219a5d2f4
+  languageName: node
+  linkType: hard
+
 "fastify-plugin@npm:^4.0.0, fastify-plugin@npm:^4.2.1":
   version: 4.5.1
   resolution: "fastify-plugin@npm:4.5.1"
@@ -3335,6 +3346,7 @@ __metadata:
     "@types/node": "npm:^18.0.0"
     dotenv: "npm:^16.0.0"
     eslint: "npm:^8.0.0"
+    fast-xml-parser: "npm:^5.3.5"
     fastify: "npm:^4.28.0"
     pino: "npm:^8.0.0"
     prettier: "npm:^2.8.0"
@@ -3773,6 +3785,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"strnum@npm:^2.1.2":
+  version: 2.1.2
+  resolution: "strnum@npm:2.1.2"
+  checksum: 10c0/4e04753b793540d79cd13b2c3e59e298440477bae2b853ab78d548138385193b37d766d95b63b7046475d68d44fb1fca692f0a3f72b03f4168af076c7b246df9
+  languageName: node
+  linkType: hard
+
 "supports-color@npm:^7.1.0":
   version: 7.2.0
   resolution: "supports-color@npm:7.2.0"