[SizzleUnrlsd]

Part 1 of #240. sys.path and getattr(...)() are left for a next step.

Summary

New sinks:

• importlib.import_module, __import__, importlib.__import__, runpy.run_module and runpy.run_path are CODE sinks.
• Only the argument naming the module or the file is a sink, by position or keyword (name, mod_name, path_name). The package of a relative name, the globals and the run name are data.
• __import__ was not resolved at all: BUILTIN_NAMES dropped every name starting with _. It now resolves to python.builtins.__import__.

How findings are reported:

• Findings are titled Untrusted module import or Untrusted script execution; the rule id stays code-injection.
• A constant package prefix ("app.plugins." + name, f-string) gives a hotspot. Reading it needs ir.ssa and abstract.module_strings, as in ssrf, so the manifest and the requires assertion in tests/test_detectors.py change accordingly.
• As decided in code-injection: dynamic imports and runpy are not modelled as sinks #240, the environment and the command line reach these sinks as they reach eval.

Verification

• tests/test_dynamic_import_sinks.py, new: 20 tests, 13 of which fail on main. They also cover negative cases (constant name, allowlist, data arguments only) and pin that eval still reports environment and command-line input.
• Full suite green, apart from the local test_packaging metadata issue. ruff check and mypy clean.
• Regression suite: no snapshot change.