Improve dev host handling and clarify backend port configuration (#532)

* fix: remove --host from npm run server command

Running `vite --host` exposes the dev server on all interfaces. However,
we should expose it on all interfaces only when `HOST` is set to `0.0.0.0`.
Otherwise, we should assume the user wants to bind to a host of their choice
and not expose the server on the network.

* fix: use src hostname for redirecting to Vite in development

Previously, the server redirected to Vite using `localhost` as the hostname.
Even if the user was using HOST="0.0.0.0", if they connected to server from
another device on the same network using `http://<host_ip>:3001`, the
server would redirect them to `http://localhost:5173`, which would not
work since `localhost` would resolve to the client's machine instead of the server.

* fix: use shared network hosts configuration for better proxy setup

- Normalize all localhost variants to 'localhost' for consistent proxy
configuration in Vite and server setup.
- use one source of truth for network hosts functions by moving them to
a shared
- log production and development urls

* refactor: rename PORT to SERVER_PORT for clarity

* chore: add comments explaining host normalization

* fix: add legacy PORT env fallback for server port configuration

* fix: add fallback for SERVER_PORT using PORT environment variable

---------

Co-authored-by: Haileyesus <something@gmail.com>
Co-authored-by: Simos Mikelatos <simosmik@gmail.com>

package.json

@@ -26,7 +26,7 @@
   "scripts": {
     "dev": "concurrently --kill-others \"npm run server\" \"npm run client\"",
     "server": "node server/index.js",
-    "client": "vite --host",
+    "client": "vite",
     "build": "vite build",
     "preview": "vite preview",
     "typecheck": "tsc --noEmit -p tsconfig.json",