feat: add bun 1.3 support

[mattppal]

Why

Bun was using a custom override (pkgs/bun/default.nix) to pin a specific version downloaded from GitHub releases. This is unnecessary since nixpkgs already provides up-to-date Bun packages.

What changed

• Deleted pkgs/bun/default.nix
  Removed the custom override that pinned Bun to 1.2.16.

• Updated pkgs/modules/bun/default.nix
  Changed to a curried function pattern ({ bun }:) to accept bun as a parameter, matching Node.js and PostgreSQL modules.

• Updated pkgs/modules/default.nix
  Now passes pkgs.bun explicitly to the Bun module.

• Updated pkgs/modules/nodejs/default.nix
  Changed pkgs.callPackage ../../bun { } to pkgs.bun.

• Added bun-1.2 to pkgs/historical-modules/default.nix
  Pinned to commit a3a6925 with displayVersion = 1.2.16 for backwards compatibility.

• Updated pkgs/upgrade-map/default.nix
  Added upgrade chain:
  bun-1.0 → bun-1.1 → bun-1.2 → bun-1.3

Test plan

nix fmt -- --check .

nix eval .#activeModules --apply 'builtins.attrNames' --json | grep bun
# Shows "bun-1.3"

nix eval .#modules --apply 'builtins.attrNames' --json | grep bun
# Shows bun-1.0 through bun-1.3

nix eval '.#activeModules."bun-1.3"'
# Evaluates successfully

[masad-frost]

Looks good to me, but probably best to wait for Ryan's stamp