Monorepo: consolidate 7 repos into one

Combines shared, blog, market, cart, events, federation, and account
into a single repository. Eliminates submodule sync, sibling model
copying at build time, and per-app CI orchestration.

Changes:
- Remove per-app .git, .gitmodules, .gitea, submodule shared/ dirs
- Remove stale sibling model copies from each app
- Update all 6 Dockerfiles for monorepo build context (root = .)
- Add build directives to docker-compose.yml
- Add single .gitea/workflows/ci.yml with change detection
- Add .dockerignore for monorepo build context
- Create __init__.py for federation and account (cross-app imports)

market/scrape/build_snapshot/tools/rewrite_nav.py

@@ -0,0 +1,24 @@
+
+from typing import Dict
+from urllib.parse import urljoin
+from shared.config import config
+
+def rewrite_nav(nav: Dict[str, Dict], nav_redirects:Dict[str, str]):
+    if nav_redirects:
+      for label, data in (nav.get("cats") or {}).items():
+          top_slug = (data or {}).get("slug")
+          if not top_slug:
+              continue
+          new_subs = []
+          for s in (data.get("subs") or []):
+              old_sub = (s.get("slug") or "").strip()
+              if not old_sub:
+                  continue
+              old_path = f"/{top_slug}/{old_sub}"
+              canonical_path = nav_redirects.get(old_path, old_path)
+              parts = [x for x in canonical_path.split("/") if x]
+              top2, sub2 = parts[0], parts[1]
+              s["slug"] = sub2
+              s["href"] = urljoin(config()["base_url"], f"/{top2}/{sub2}")
+              new_subs.append(s)
+          data["subs"] = new_subs