feat: serve docs flat at /<repo>/ with no redirects

- collect.py copies each repo's built site contents directly to a
  top-level <repo>/ dir (was libs|apis|wiki/<repo>/site nesting)
- nginx uses `index index.html lib/index.html api/index.html` so
  /dagpipe/ -> lib/index.html, /auth-server/ -> api/index.html are
  served internally with no redirects
- _index regenerates links against the flat layout
  (/dagpipe/lib/, /auth-server/api/, /mongo-ops/, /blog/...)
- config.yml static entries point at vendored blog/ + media-manager/
- Dockerfile copies per-repo dirs flat into the nginx html root
- removed stale libs/, apis/, wiki/, tutorials/ category trees

config.yml

@@ -6,10 +6,10 @@
 #   static:  docs already vendored inside this repository (never collected)
 #
 # Each repo may provide any of the doc kinds: lib, api, wiki (web sites) and mcp (MCP bundle).
-# Category -> served path:
-#   lib  -> /libs/<repo>/
-#   api  -> /apis/<repo>/
-#   wiki -> /wiki/<repo>/
+# Served layout (flat, one dir per repo; no redirects):
+#   lib  -> /<repo>/lib/
+#   api  -> /<repo>/api/   (or /<repo>/ when the site has a root index.html)
+#   wiki -> /<repo>/
 #   mcp  -> MCP server on its configured port
 
 service:
@@ -92,10 +92,10 @@ static:
     repo: blog
     title: Blog API
     description: A modular, async Blog API backend for FastAPI microservices. Provides streamlined CRUD operations for articles and authors.
-    path: apis/blog/site
+    path: blog
 
   - kind: tutorial
     repo: media-manager
     title: Media Manager Tutorial
     description: Step-by-step guide to the Media Manager architecture, ingestion pipeline, automation workflows, and integrations.
-    path: tutorials/media-manager/site
+    path: media-manager