Add Solidity linting with solhint, Foundry formatter, and pre-commit hooks (#51)

## Changes

### Configuration
- Added .solhint.json with recommended rules + custom config
  - 160 char line length (warn)
  - Double quotes enforcement (error)
  - Explicit visibility required (error)
  - Console statements allowed (scripts/tests need them)
  - Gas optimization warnings enabled
  - Ignores test/helpers/, lib/, out/, cache/, broadcast/

- Added foundry.toml [fmt] section
  - 160 char line length
  - 4-space tabs
  - Double quotes
  - Thousands separators for numbers
  - Sort imports enabled

- Added .lintstagedrc.json for pre-commit auto-fix
  - Runs solhint --fix on .sol files
  - Runs forge fmt on .sol files

- Added husky pre-commit hook via lint-staged

### NPM Scripts
- lint:sol - run solhint
- lint:sol:fix - auto-fix solhint issues
- format:sol - format with forge fmt
- format:sol:check - check formatting
- lint / lint:fix - combined commands

### Code Changes
- Added explicit visibility modifiers (internal) to constants in scripts and tests
- Fixed quote style in DeployLocal.sol
- All Solidity files formatted with forge fmt

## Verification
- ✅ forge fmt --check passes
- ✅ No solhint errors (warnings only)
- ✅ forge build succeeds
- ✅ forge test passes (107/107)

resolves #44

Co-authored-by: johba <johba@harb.eth>
Reviewed-on: https://codeberg.org/johba/harb/pulls/51

onchain/script/DeployBase.sol

@@ -1,15 +1,16 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 pragma solidity ^0.8.19;
 
-import "forge-std/Script.sol";
+import "../src/Kraiken.sol";
+
+import { LiquidityManager } from "../src/LiquidityManager.sol";
+import "../src/Optimizer.sol";
+import "../src/Stake.sol";
+import "../src/helpers/UniswapHelpers.sol";
+import { ERC1967Proxy } from "@openzeppelin/proxy/ERC1967/ERC1967Proxy.sol";
 import "@uniswap-v3-core/interfaces/IUniswapV3Factory.sol";
 import "@uniswap-v3-core/interfaces/IUniswapV3Pool.sol";
-import "../src/Kraiken.sol";
-import "../src/Stake.sol";
-import "../src/Optimizer.sol";
-import "../src/helpers/UniswapHelpers.sol";
-import {LiquidityManager} from "../src/LiquidityManager.sol";
-import {ERC1967Proxy} from "@openzeppelin/proxy/ERC1967/ERC1967Proxy.sol";
+import "forge-std/Script.sol";
 
 uint24 constant FEE = uint24(10_000);
 
@@ -74,11 +75,7 @@ contract DeployBase is Script {
         address optimizerAddress;
         if (optimizer == address(0)) {
             Optimizer optimizerImpl = new Optimizer();
-            bytes memory params = abi.encodeWithSignature(
-                "initialize(address,address)",
-                address(kraiken),
-                address(stake)
-            );
+            bytes memory params = abi.encodeWithSignature("initialize(address,address)", address(kraiken), address(stake));
             ERC1967Proxy proxy = new ERC1967Proxy(address(optimizerImpl), params);
             optimizerAddress = address(proxy);
             console.log("Optimizer deployed at:", optimizerAddress);
@@ -88,12 +85,7 @@ contract DeployBase is Script {
         }
 
         // Deploy LiquidityManager
-        liquidityManager = new LiquidityManager(
-            v3Factory,
-            weth,
-            address(kraiken),
-            optimizerAddress
-        );
+        liquidityManager = new LiquidityManager(v3Factory, weth, address(kraiken), optimizerAddress);
         console.log("LiquidityManager deployed at:", address(liquidityManager));
 
         // Set fee destination
@@ -115,4 +107,4 @@ contract DeployBase is Script {
 
         vm.stopBroadcast();
     }
-}
+}