Initial boilerplate scaffold for continuum-schemas

Protobuf data model (Template/PrintJob/MaterialProfile/PrintParameters)
with codegen targets for TypeBox+TS types (packages/ts-types) and
prost-derived Rust structs (packages/rust-types).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

proto/continuum/v1/template.proto

@@ -0,0 +1,19 @@
+syntax = "proto3";
+
+package continuum.v1;
+
+import "continuum/v1/material.proto";
+import "continuum/v1/print_params.proto";
+
+message Template {
+  string id = 1;
+  string name = 2;
+  string description = 3;
+  string owner_id = 4;
+  string model_file_key = 5;
+  MaterialProfile material = 6;
+  PrintParameters print_parameters = 7;
+  int64 created_at_unix = 8;
+  int64 updated_at_unix = 9;
+  repeated string tags = 10;
+}