feat(security): SEC004 + SEC007 multi-language dispatch (PR #18)

[wei9072]

Summary

Closes the audit gaps in SEC003-008 noted after PRs #10 / #12.
Two rules had real coverage gaps; the others were already decent.

Rule	Coverage before	Action
SEC003 TLS off	text Python / Node / Go / .NET	☑ unchanged
SEC004 shell	Python `shell=True` only	✅ language-aware dispatch
SEC005 SQL concat	Python / Java decent	☑ unchanged
SEC006 CORS	text cross-language	☑ unchanged
SEC007 JWT	`name.contains("jwt")` — Python only	✅ language-aware dispatch
SEC008 deser	Python / Node / Java decent	☑ unchanged

SEC004 expansion

Language	Catch shape
Python	subprocess.run / Popen with `shell=True` + interp
Node.js	`child_process.exec` / `execSync` + interp (always shells)
PHP	global `shell_exec` / `exec` / `passthru` / `system` / `proc_open` + interp
Java	`Runtime.exec(String)` overload + concat (String[] overload safe)
Go	`exec.Command("sh", "-c", ...)` + interp; bare `exec.Command("ls", arg)` safe

`text_has_interp` extended with PHP `.` concat (gated on `$` to
avoid floating-point literals).

SEC007 expansion

Language	Catch shape
Python	`jwt.decode(...)` without algorithms/key/verify (existing)
Node.js	`jsonwebtoken.decode()` always unverified; `verify()` with `verify:false` opt
Java / Kotlin	`JWT.decode(token)` returns unverified DecodedJWT (Auth0 lib)
PHP	`JWT::decode` without explicit algorithm list

`check_jwt_unsafe` now takes `&ParsedFile` so language identity
is available — prevents PHP `JWT::decode` from being misclassified
as Java (the old `name.contains("JWT")` check was language-blind).

Infrastructure

• `call_name` extended for PHP: now handles
  `scoped_call_expression` (`Class::method`) and
  `member_call_expression` (`$obj->method`). Previously these
  fell back to `named_child(0)` and returned just the receiver.
• `leaf_method_name(name)` helper splits on `.` / `::` /
  `->` so leaf-method matching works across all four conventions.
• walk dispatch picks up `scoped_call_expression` +
  `member_call_expression` node kinds.

Tests

10 new tests (5 SEC004 + 5 SEC007 covering Python / Node / PHP /
Java / Go). 174 → 177 total tests pass.

Test plan

• `cargo test --workspace` — 177 / 177 pass
• PHP scoped + member call shapes recognised by `call_name`
• No language-blind FP between Java JWT and PHP JWT
  (each only fires on its own language)
• Bare `exec.Command("ls", arg)` Go pattern stays silent
  (positive negative)
• `child_process.exec('ls -la')` static-string stays silent
• CI green on push

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