Remove HA/Python components and add Phoenix LiveView dashboard

- Remove home-assistant-integration/ and dev-config/
- Remove Python/HA dependencies from flake.nix
- Add Phoenix LiveView dashboard with clean Elixir-only stack
- Add Node.js and PostgreSQL for Phoenix development
- Much cleaner monorepo architecture focusing on Elixir ecosystem

Next: Connect dashboard to MQTT for real-time host monitoring

server/dashboard/priv/gettext/en/LC_MESSAGES/errors.po

@@ -0,0 +1,11 @@
+## `msgid`s in this file come from POT (.pot) files.
+##
+## Do not add, change, or remove `msgid`s manually here as
+## they're tied to the ones in the corresponding POT file
+## (with the same domain).
+##
+## Use `mix gettext.extract --merge` or `mix gettext.merge`
+## to merge POT files into PO files.
+msgid ""
+msgstr ""
+"Language: en\n"