Add mise configuration for local toolchain management

Sets up `mise` for automatic Java + Maven provisioning, matching the
pattern already in use in minfraud-api-dotnet and GeoIP2-dotnet. This
lets contributors run the full test/lint loop locally without manually
installing a JDK or Maven.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: oschwald

mise.lock

@@ -0,0 +1,18 @@
+[settings]
+experimental = true
+lockfile = true
+disable_backends = [
+    "asdf",
+    "vfox",
+]
+
+[tools]
+java = "latest"
+maven = "latest"
+
+[hooks]
+enter = "mise install --quiet --locked"
+
+[[watch_files]]
+patterns = ["mise.toml", "mise.lock"]
+run = "mise install --quiet --locked"