feat(realism): wire fingerprint_html/svg through taxonomy + UI

The two new fingerprint canary generators existed at the API level
since f64e78f but weren't visible to the realism engine or the
operator-facing dashboard. Threads them through every place that
enumerates canary content classes.

Backend:
* realism/taxonomy.py - two new ContentClass members
  (CANARY_FINGERPRINT_HTML, CANARY_FINGERPRINT_SVG); enum is
  wire-visible (synthetic_files.content_class column + bus discrim)
  so we add at the bottom, never reorder.
* canary/cultivator.py - class-to-generator dispatch, kind mapping
  (both http), and default placement paths
  (~/Documents/asset_directory.html and network_topology.svg).
* realism/naming.py + bodies.py - _name_canary / _body_canary entries.
* realism/planner.py - added to _DEFAULT_CANARY_CLASS_WEIGHTS and
  the _CANARY_CLASSES classification set.

Frontend:
* decnet_web/src/realism/labels.ts - display labels.
* decnet_web/src/components/RealismConfig/RealismConfig.tsx - default
  canary weight rows so operators see them in the realism config UI.
* decnet_web/src/components/SyntheticFiles/SyntheticFiles.tsx - added
  to the CONTENT_CLASSES allow-list so filter dropdowns show them.

Also: re-applied the nosec B404/B603 markers on canary/obfuscator.py;
the first commit's pre-commit autoformatter stripped them.

Tests: extended tests/realism/test_taxonomy.py's stability assertion
to include the two new values. Full canary + realism suites pass
(362 / 2 skipped).

tests/realism/test_taxonomy.py

@@ -26,6 +26,7 @@ def test_content_class_values_are_stable() -> None:
         "canary_aws_creds", "canary_env_file", "canary_git_config",
         "canary_ssh_key", "canary_honeydoc", "canary_honeydoc_docx",
         "canary_honeydoc_pdf", "canary_mysql_dump",
+        "canary_fingerprint_html", "canary_fingerprint_svg",
     }