Vendor @keysat/licensing-client to avoid private-repo auth in Docker build

The keysat-client-ts repo is private. Previous builds were succeeding
purely because Docker layer caching reused a node_modules from when
the repo had been accessible — once anything invalidated the
server/package.json or server/package-lock.json hash (the rename did),
npm in a fresh container hit github with no credentials and 404'd.

Fix: copy the built dist/ from server/node_modules/@keysat/licensing-
client/ into vendor/keysat-licensing-client/, strip the prepare/build
scripts (we already have the compiled output), and switch the server
package.json dep to a file: path:

  "@keysat/licensing-client": "file:../vendor/keysat-licensing-client"

Dockerfile now COPY's vendor/ before npm ci. No git, no SSH, no
credentials needed in the build container — and the npm step is
pure-local so it's deterministic.

Side cleanup: dropped the apt-install-git + url.insteadOf gymnastics
that existed solely to work around the now-removed git+https resolution.
The image is slightly smaller (no git in the builder stage). Switched
the npm flag to the modern --omit=dev (the legacy --production printed
a warning).

If keysat-client-ts updates, regenerate vendor/ by:

  cp -r server/node_modules/@keysat/licensing-client/{dist,package.json,LICENSE,README.md} \
        vendor/keysat-licensing-client/
  # then strip prepare/build scripts and devDeps from the copied package.json
  # (or just hand-edit if the upstream package.json hasn't changed)

vendor/keysat-licensing-client/package.json

@@ -0,0 +1,33 @@
+{
+  "name": "@keysat/licensing-client",
+  "version": "0.1.0",
+  "description": "Client library for Keysat. Verifies signed license keys offline and wraps the HTTP API for purchase and revocation checks.",
+  "type": "module",
+  "main": "./dist/index.cjs",
+  "module": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js",
+      "require": "./dist/index.cjs"
+    }
+  },
+  "files": ["dist", "README.md", "LICENSE"],
+  "scripts": {},
+  "keywords": [
+    "bitcoin",
+    "licensing",
+    "btcpay",
+    "start9",
+    "ed25519"
+  ],
+  "repository": "https://github.com/keysat-xyz/keysat-client-ts",
+  "license": "MIT",
+  "engines": { "node": ">=18" },
+  "dependencies": {
+    "@noble/ed25519": "^2.0.0",
+    "@noble/hashes": "^1.3.3"
+  },
+  "devDependencies": {}
+}