Reduce docker image size with multi-stage build and dependency pruning (#1581)

## Description:
This PR focuses on trimming down docker image size while keeping runtime
behaviour intact.
This partially addresses #1242 by slimming the production Docker image
by ~33%.
```
$ docker image ls | grep openfront
openfrontio  latest   992fb420f131   1 minute ago   1.05GB   # new
evanpelle/openfront-prod <none> 216c629def78 6 hours ago 1.58GB   # current prod
```

The savings come from three areas:
- Refactor `Dockerfile` into a three‑stage build (dependencies / build /
runtime).
- Installs dev‑only node packages in a throw‑away layer and copies only
production modules to the final image.
- Updated `webpack.config.js` to skip copying `resources/maps/**/*`
which never referenced by the client.

Because the current codebase does not cleanly separate dev/prod
requirements, extensive regression testing is necessary; some latent
prod usage of dev‑only modules might surface.

## Please complete the following:
- [X] I have added screenshots for all UI updates
- [X] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [X] I have added relevant tests to the test directory
- [X] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [X] I have read and accepted the CLA agreement (only required once).

## Please put your Discord username so you can be contacted if a bug or
regression is found:

aaa4xu

---------

Co-authored-by: Scott Anderson <662325+scottanderson@users.noreply.github.com>

package.json

@@ -31,9 +31,13 @@
     "@types/benchmark": "^2.1.5",
     "@types/chai": "^4.3.17",
     "@types/d3": "^7.4.3",
+    "@types/express": "^4.17.23",
+    "@types/google-protobuf": "^3.15.12",
+    "@types/hammerjs": "^2.0.46",
     "@types/jest": "^30.0.0",
     "@types/jquery": "^3.5.31",
     "@types/js-yaml": "^4.0.9",
+    "@types/msgpack5": "^3.4.6",
     "@types/node": "^22.10.2",
     "@types/pg": "^8.11.11",
     "@types/sinon": "^17.0.3",
@@ -45,6 +49,7 @@
     "canvas": "^3.1.0",
     "chai": "^5.1.1",
     "concurrently": "^8.2.2",
+    "copy-webpack-plugin": "^13.0.0",
     "cross-env": "^7.0.3",
     "css-loader": "^7.1.2",
     "eslint": "^9.21.0",
@@ -55,6 +60,7 @@
     "globals": "^16.0.0",
     "html-inline-script-webpack-plugin": "^3.2.1",
     "html-loader": "^5.1.0",
+    "html-webpack-plugin": "^5.6.3",
     "husky": "^9.1.7",
     "jest": "^30.0.0",
     "jest-environment-jsdom": "^30.0.0",
@@ -72,11 +78,13 @@
     "tailwindcss": "^3.4.17",
     "ts-jest": "^29.2.4",
     "ts-loader": "^9.5.2",
-    "ts-node": "^10.9.2",
     "tsconfig-paths": "^4.2.0",
     "tsx": "^4.17.0",
     "typescript": "^5.7.2",
     "typescript-eslint": "^8.26.0",
+    "webpack": "^5.100.2",
+    "webpack-cli": "^6.0.1",
+    "webpack-dev-server": "^5.2.2",
     "worker-loader": "^3.0.8"
   },
   "dependencies": {
@@ -97,14 +105,9 @@
     "@opentelemetry/semantic-conventions": "^1.32.0",
     "@opentelemetry/winston-transport": "^0.11.0",
     "@stripe/stripe-js": "^7.4.0",
-    "@types/express": "^4.17.21",
-    "@types/google-protobuf": "^3.15.12",
-    "@types/hammerjs": "^2.0.45",
-    "@types/msgpack5": "^3.4.6",
     "binary-loader": "^0.0.1",
     "colord": "^2.9.3",
     "colorjs.io": "^0.5.2",
-    "copy-webpack-plugin": "^13.0.0",
     "d3": "^7.9.0",
     "dompurify": "^3.1.7",
     "dotenv": "^16.5.0",
@@ -114,10 +117,10 @@
     "google-auth-library": "^9.14.0",
     "googleapis": "^143.0.0",
     "hammerjs": "^2.0.8",
-    "html-webpack-plugin": "^5.6.3",
     "ip-anonymize": "^0.1.0",
     "jimp": "^0.22.12",
     "jose": "^6.0.10",
+    "js-yaml": "^4.1.0",
     "lit": "^3.2.1",
     "lit-markdown": "^1.3.2",
     "msgpack5": "^6.0.2",
@@ -131,11 +134,9 @@
     "pureimage": "^0.4.13",
     "sharp": "^0.34.2",
     "systeminformation": "^5.25.11",
+    "ts-node": "^10.9.2",
     "twemoji": "^14.0.2",
     "uuid": "^11.1.0",
-    "webpack": "^5.91.0",
-    "webpack-cli": "^6.0.1",
-    "webpack-dev-server": "^5.2.2",
     "winston": "^3.17.0",
     "winston-transport": "^4.9.0",
     "ws": "^8.18.0",