feat: initial implementation of content-addressed incremental backup engine

Rust-centric architecture with TypeScript facade following smartproxy/smartstorage pattern.
Core engine in Rust (FastCDC chunking, SHA-256, gzip, AES-256-GCM + Argon2id, binary pack files,
global index, snapshots, locking, verification, pruning, repair). TypeScript provides npm interface
via @push.rocks/smartrust RustBridge IPC with Unix socket streaming for ingest/restore.
All 14 integration tests pass.

tsconfig.json

@@ -0,0 +1,14 @@
+{
+  "compilerOptions": {
+    "experimentalDecorators": true,
+    "useDefineForClassFields": false,
+    "target": "ES2022",
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "esModuleInterop": true,
+    "verbatimModuleSyntax": true
+  },
+  "exclude": [
+    "dist_*/**/*.d.ts"
+  ]
+}