fix(api): normalize trailing slashes — no slash on param routes

Rule: trailing slash only on collection roots (/). Any route containing
a path parameter {…} uses no trailing slash. Applies across all routers,
scripts, Makefile, and tests. Fixes 307-redirect fragility on POST/PATCH
from naive clients (curl, Codex HTTP calls).

Also adds POST /repos/{slug}/sync — runs ADR-001 consistency check with
--fix via HTTP, so non-MCP agents (Codex) can self-service DB sync without
operator intervention.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/check_doi.py

@@ -69,7 +69,7 @@ def _print_report(report, use_color: bool = True) -> None:
 
 async def check_repo(slug: str, as_json: bool) -> bool:
     try:
-        repo = _get(f"/repos/{slug}/")
+        repo = _get(f"/repos/{slug}")
     except Exception as e:
         print(f"✗ Could not fetch repo '{slug}': {e}", file=sys.stderr)
         return False