n8n: add backend endpoints for the RAGcore Procedure Sync workflow

GET /api/v1/integrations/n8n/procedures lists every procedure Markdown
file Fleet Ops ships (all languages) with a stable per-document id and
content hash, ready for workflow 3 to push into RAGcore. POST
.../procedures-sync-result records the sync outcome as an idempotent
audit event, matching the existing return-callback/workflow-error
pattern. Extracted frontmatter parsing out of the demo knowledge
provider into a shared module so both read the same source of truth.

backend/app/services/knowledge/demo.py

@@ -7,6 +7,7 @@ from pathlib import Path
 
 from app.core.config import get_settings
 from app.services.knowledge import GroundedAnswer, KnowledgeHealth, SourceCard
+from app.services.knowledge.procedures import parse_frontmatter
 
 SUPPORTED_LANGUAGES = ("nl-BE", "en-GB", "fr-BE")
 DEFAULT_LANGUAGE = "en-GB"
@@ -74,23 +75,6 @@ class ScoredSection:
     body_tokens: set[str]
 
 
-def _parse_frontmatter(raw: str) -> tuple[dict[str, str], str]:
-    if not raw.startswith("---"):
-        return {}, raw
-    end = raw.find("\n---", 3)
-    if end == -1:
-        return {}, raw
-    block = raw[3:end].strip()
-    body = raw[end + 4 :].lstrip("\n")
-    meta: dict[str, str] = {}
-    for line in block.splitlines():
-        if ":" not in line:
-            continue
-        key, _, value = line.partition(":")
-        meta[key.strip()] = value.strip().strip('"')
-    return meta, body
-
-
 def _split_sections(body: str) -> list[tuple[str, str]]:
     sections: list[tuple[str, str]] = []
     current_heading = "Overview"
@@ -114,7 +98,7 @@ def _load_sections(procedures_dir: Path, language: str) -> list[ScoredSection]:
     sections: list[ScoredSection] = []
     for path in sorted(procedures_dir.glob("*.md")):
         raw = path.read_text(encoding="utf-8")
-        meta, body = _parse_frontmatter(raw)
+        meta, body = parse_frontmatter(raw)
         title = meta.get("title", path.stem)
         doc = Document(
             document_id=meta.get("document_id", path.stem),