fix: remove unnecessary zero value initialization (revive)

- Remove explicit = 0 from uint32 declaration as it's the default zero value

.claude/settings.local.json

@@ -16,7 +16,8 @@
       "Bash(git add:*)",
       "Bash(gofumpt:*)",
       "Bash(git stash:*)",
-      "Bash(git commit:*)"
+      "Bash(git commit:*)",
+      "Bash(git push:*)"
     ],
     "deny": []
   }

internal/vault/metadata.go

@@ -85,7 +85,7 @@ func GetNextDerivationIndex(fs afero.Fs, stateDir string, mnemonic string) (uint
 	}
 
 	// Find the first available index
-	var index uint32 = 0
+	var index uint32
 	for usedIndices[index] {
 		index++
 	}