Add runtime regex check configuration

[xiaoshuai7038]

Implements runtime regex alerts loaded from a JSON config file via --checks / --check-config.

Summary:

• Supports config as either a JSON array or an object with a checks array.
• Validates required field, regex, and alert values, unsupported fields, invalid regexes, and bad case-sensitivity flags.
• Supports domain, DNS record, HTTP status/content-length/code-string, and response body fields.
• Keeps response bodies only in memory for matching, capped at 64 KiB, and does not write bodies to result JSON.
• Adds README docs, an example config, and a lightweight parser test target behind DOOKED_BUILD_TESTS.

Validation:

• git diff --check
• python3 -m json.tool dooked/examples/regex-checks.json >/dev/null
• clang++ -std=c++17 -Idooked/include -Idooked/json/include -Idooked/spdlog/include dooked/test/regex_checks_test.cpp dooked/source/checks/regex_checks.cpp dooked/source/utils/constants.cpp dooked/source/utils/string_utils.cpp -o /tmp/dooked_regex_checks_test && /tmp/dooked_regex_checks_test

Full CMake validation was not possible in this environment because cmake is unavailable. Dependency submodules were initialized for the standalone parser test.

Fixes #2

If this is selected for the listed bounty, my PayPal link is: https://paypal.me/xiaoshuai12138