luacheck caught that `k` was being set as a global variable instead of
local in two places in item-providers-util.lua. This could potentially
cause subtle bugs if the global `k` was read elsewhere.

Configure stylua formatter with:
- 2-space indentation (matching modern Factorio mod conventions)
- 120 character column width
- Unix line endings
- Auto-prefer double quotes

Reformatted all 57 Lua files using stylua with:
- 2-space indentation (was tabs)
- 120 character column width
- Unix line endings
- Double quotes preferred

This is a pure formatting change with no logic modifications.
Use .git-blame-ignore-revs to skip this commit in git blame.

Allows git blame to look through the stylua formatting commit.
Configure with: git config blame.ignoreRevsFile .git-blame-ignore-revs

Runs on push to master and all PRs:
- luacheck: static analysis for undefined globals, wrong API usage
- stylua: formatting check (2-space indent, 120 col width)

`not x == false` is parsed as `(not x) == false` due to operator
precedence. Changed to `x ~= false` which expresses the intent clearly.
Caught by luacheck W582 in CI.