chore(deps): update dependency solhint to v6 (#159)

This PR contains the following updates:

| Package | Type | Update | Change | OpenSSF |
|---|---|---|---|---|
| [solhint](https://protofire.github.io/solhint/)
([source](https://redirect.github.com/protofire/solhint)) | dependencies
| major | [`5.2.0` ->
`6.0.0`](https://renovatebot.com/diffs/npm/solhint/5.2.0/6.0.0) |
[![OpenSSF
Scorecard](https://api.securityscorecards.dev/projects/github.com/protofire/solhint/badge)](https://securityscorecards.dev/viewer/?uri=github.com/protofire/solhint)
|

---

### Release Notes

<details>
<summary>protofire/solhint (solhint)</summary>

###
[`v6.0.0`](https://redirect.github.com/protofire/solhint/blob/HEAD/CHANGELOG.md#600---2025-07-04)

[Compare
Source](https://redirect.github.com/protofire/solhint/compare/v5.2.0...v6.0.0)

##### BREAKING CHANGE

Some rules were removed from the recommended ruleset and other were
promoted. See below:
Rules revision -
[#&#8203;692](https://redirect.github.com/protofire/solhint/pull/692)

##### 🟥 DEMOTED

- `payable-fallback`: Outdated due to the introduction of receive();
rarely needed in modern Solidity.
  <br>

##### ✅ PROMOTED

- `interface-starts-with-i`: Promotes clarity by clearly distinguishing
interfaces from contracts.
- `gas-calldata-parameters`: Encourages optimal memory usage for
external functions.
- `gas-increment-by-one`: Suggests using ++i style for gas-efficient
increments.
- `gas-indexed-events`: Improves event indexing for off-chain systems
and reduces gas usage.
- `gas-small-strings`: Recommends cheaper encoding using bytes32 for
short strings.
- `gas-strict-inequalities`: Helps avoid subtle off-by-one bugs in range
conditions.
- `gas-struct-packing`: Maximizes storage efficiency by suggesting tight
struct packing.
- `duplicated-imports`: Prevents redundant imports that bloat the AST
and confuse code structure.
- `import-path-check`: Ensures all imported files exist and resolve
correctly, avoiding runtime errors.
- `function-max-lines`: Encourages smaller, more readable and
maintainable functions.
- `constructor-syntax`: Enforces modern constructor syntax for
consistency and clarity.
- `use-natspec`: Promotes proper documentation with NatSpec for better
audits and readability.

##### Fixed

- `gas-struct-packing` false positives -
[#&#8203;690](https://redirect.github.com/protofire/solhint/pull/690)
- `gas-increment-by-one` backward expression -
[#&#8203;691](https://redirect.github.com/protofire/solhint/pull/691)
- Typo (thanks to
@&#8203;[MarkFizz77](https://redirect.github.com/MarkFizz77))

##### Added

- `use-natspec`: Promote the use of natspec and make several checks to
enforce it -
[#&#8203;689](https://redirect.github.com/protofire/solhint/pull/689)

<br><br>

</details>

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bun.lock

@@ -41,7 +41,7 @@
     "@nomicfoundation/hardhat-toolbox-viem": "3.0.0",
     "@nomiclabs/hardhat-solhint": "4.1.0",
     "hardhat": "2.26.1",
-    "solhint": "5.2.0",
+    "solhint": "6.0.0",
     "@openzeppelin/subgraphs": "0.1.8-5"
   },
   "overrides": {