Fix Docker production build: move tsx to dependencies, reinstall in production stage

The production Docker stage was copying pnpm symlinks between stages
which broke module resolution. Now does a fresh pnpm install --prod
in the production stage and runs from the server working directory.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pnpm-lock.yaml

@@ -38,6 +38,9 @@ importers:
       postgres:
         specifier: ^3.4.7
         version: 3.4.9
+      tsx:
+        specifier: ^4.19.4
+        version: 4.21.0
       uuid:
         specifier: ^11.1.0
         version: 11.1.0
@@ -51,9 +54,6 @@ importers:
       drizzle-kit:
         specifier: ^0.31.1
         version: 0.31.10
-      tsx:
-        specifier: ^4.19.4
-        version: 4.21.0
       typescript:
         specifier: ^5.8.3
         version: 5.9.3