fix(build): declare tz-lookup as a client dependency

It was present in the lockfile but undeclared, so the local install had it
while the Docker client build (npm ci --workspace=client) did not.

client/package.json

@@ -52,6 +52,7 @@
     "remark-breaks": "^4.0.0",
     "remark-gfm": "^4.0.1",
     "topojson-client": "^3.1.0",
+    "tz-lookup": "^6.1.25",
     "zod": "^4.3.6",
     "zustand": "^4.5.2"
   },

package-lock.json

@@ -54,6 +54,7 @@
         "remark-breaks": "^4.0.0",
         "remark-gfm": "^4.0.1",
         "topojson-client": "^3.1.0",
+        "tz-lookup": "^6.1.25",
         "zod": "^4.3.6",
         "zustand": "^4.5.2"
       },
@@ -19336,7 +19337,6 @@
       "version": "6.1.25",
       "resolved": "https://registry.npmjs.org/tz-lookup/-/tz-lookup-6.1.25.tgz",
       "integrity": "sha512-fFewT9o1uDzsW1QnUU1ValqaihFnwiUiiHr1S79/fxOzKXYYvX+EHeRnpvQJ9B3Qg67wPXT6QF2Esc4pFOrvLg==",
-      "dev": true,
       "license": "CC0-1.0"
     },
     "node_modules/uid": {