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>

tests/test_routers_td_ep_contrib.py

@@ -68,13 +68,13 @@ class TestTechnicalDebt:
         })
         td_id = r.json()["id"]
 
-        r2 = await client.post(f"/technical-debt/{td_id}/notes/", json={
+        r2 = await client.post(f"/technical-debt/{td_id}/notes", json={
             "step": "analysis",
             "content": "Root cause identified.",
         })
         assert r2.status_code == 201
 
-        r3 = await client.get(f"/technical-debt/{td_id}/notes/")
+        r3 = await client.get(f"/technical-debt/{td_id}/notes")
         assert r3.status_code == 200
         assert len(r3.json()) == 1