fix: exclude __Snapshots__ directories from test targets (#815)

Explicitly exclude __Snapshots__ directories from FunctionsTests,
PostgRESTTests, and StorageTests targets to resolve Swift Package
Manager warnings about unhandled files.

These snapshot files are managed by swift-snapshot-testing and should
not be processed as test resources.

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

Co-authored-by: Claude <[email protected]>

Author: Guilherme Souza

Package.swift

@@ -90,6 +90,9 @@ let package = Package(
         "Functions",
         "Mocker",
         "TestHelpers",
+      ],
+      exclude: [
+        "__Snapshots__"
       ]
     ),
     .testTarget(
@@ -123,6 +126,9 @@ let package = Package(
         "Mocker",
         "PostgREST",
         "TestHelpers",
+      ],
+      exclude: [
+        "__Snapshots__"
       ]
     ),
     .target(
@@ -160,6 +166,9 @@ let package = Package(
         "TestHelpers",
         "Storage",
       ],
+      exclude: [
+        "__Snapshots__"
+      ],
       resources: [
         .copy("sadcat.jpg"),
         .process("Fixtures"),