feat(rules): Django request sources; a destination with a fixed origin is not untrusted

python.toml's sources were Flask-only, so no flow could start anywhere on a Django
project. OpenCVE's SSRF reads its URL from `form.cleaned_data`, and the scan answered
the sink file and found nothing. Added: request.GET/POST/body/COOKIES/FILES/META,
DRF's query_params, and cleaned_data.

With those sources known, OpenCVE reported three redirects that cannot leave the
site: `reverse("cves") + "?" + request.GET.urlencode()` (twice) and
`reverse(route, kwargs=...)`. Destination sink facts can now set
`prefix_fixes_origin` and `origin_anchors`. A path is cut when it enters a
concatenation, f-string or `+=` through anything other than its leftmost operand,
and that operand fixes the origin. Origin-fixing operands:
- a literal `/x`, `?` or `#`;
- a literal of the form scheme://host/;
- an anchor call;
- a variable whose every assignment fixes the origin.
A path is also cut when it passes through an anchor. `"/" + x` (//evil) and
`"https://" + host` stay reported. A Joern-gated test covers all seven shapes.

Exploratory (retune after protocol-v1): OpenCVE vulnerable and fixed pins are both
0 findings, down from 2 and 3. The SSRF itself is still missed, because the flow
crosses a registry dispatch (`REGISTRY.get(t)(extras).run()`) that the engine does
not follow.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01EmM1j46qgKMh3zqD1QMwEo

src/openultrasast/ruleset/semantic/javascript.toml

@@ -123,12 +123,14 @@ calls = [
   "https.request",
 ]
 rule_ids = []
+prefix_fixes_origin = true
 
 [[sink]]
 id = "redirect"
 cwe = "CWE-601"
 calls = ["redirect", "location.assign", "location.replace"]
 rule_ids = []
+prefix_fixes_origin = true
 
 # --- model-grounded-detection: sanitizers -----------------------------------------------------------------
 # This file shipped with no [[sanitizer]] entries at all, so no JavaScript fix of any family could be