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).

decnet/canary/obfuscator.py

@@ -24,7 +24,7 @@ from __future__ import annotations
 import hashlib
 import json
 import os
-import subprocess
+import subprocess  # nosec B404 — Node helper exec is the whole point
 from pathlib import Path
 from typing import Any
 
@@ -103,7 +103,7 @@ def obfuscate(code: str, *, callback_token: str) -> str:
     options = _config_from_seed(seed)
     payload = json.dumps({"code": code, "options": options})
     try:
-        proc = subprocess.run(
+        proc = subprocess.run(  # nosec B603 — argv-form, no shell, fixed helper path; payload is JSON on stdin, not in argv
             [_NODE_BIN, str(_HELPER)],
             input=payload, capture_output=True, text=True,
             timeout=_TIMEOUT_S, check=False,