Modular refactor: split kraken.sh into lib/ with shellcheck-clean modules

[WhiteMuush]

Summary

• Split monolithic kraken.sh into lib/ helpers and lib/modules/ tentacles (entry point now ~130 lines)
• Drop unsafe set -e from the interactive menu (a single non-zero exit code from any wrapped tool was tearing down the loop)
• Add ensure_command / ensure_repo / prompt_value / prompt_yesno helpers - new tools integrate in ~5 lines
• Unified logger: log_step / log_info / log_warn / log_error / log_success
• TTY-aware color palette: clean output when piped to tee or files
• All globals prefixed KRAKEN_*
• Fix shellcheck SC2155 / SC2207 patterns across the codebase

What is new

• .github/workflows/ci.yml: shellcheck (warning) + bash -n on all *.sh + smoke test verifying 24 exposed functions
• .github/ISSUE_TEMPLATE/: bug report and module request templates (YAML)
• .github/PULL_REQUEST_TEMPLATE.md
• CONTRIBUTING.md, CODE_OF_CONDUCT.md, SECURITY.md
• docs/ARCHITECTURE.md: boot sequence, module contract, color model, session layout
• docs/ADDING_A_MODULE.md: step-by-step recipe with Don't / Do table
• LICENSE (MIT), .gitignore, .editorconfig

Project layout

kraken.sh                # thin entry point
lib/
  core.sh                # version, globals, TTY-aware colors
  logger.sh
  installer.sh
  ui.sh
  session.sh
  modules/
    recon.sh  scan.sh  web.sh  vuln.sh  report.sh
docs/
  ARCHITECTURE.md
  ADDING_A_MODULE.md

Test plan

• bash -n passes on all 11 *.sh files
• Smoke test: source chain + 24 expected functions present
• ./kraken.sh --help and ./kraken.sh --version work
• CI green on this PR

Notes

This branch rebuilds the repository from a clean git init. The pre-refactor history is merged in via the final Merge unrelated pre-refactor history commit, so the v1.0.0 history remains reachable from main after this PR lands.