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)

shared/browser/app/utils/parse.py

@@ -0,0 +1,36 @@
+from datetime import datetime, timezone
+
+def parse_time(val: str | None):
+    if not val:
+        return None
+    try:
+        h,m = val.split(':', 1)
+        from datetime import time
+        return time(int(h), int(m))
+    except Exception:
+        return None
+
+def parse_cost(val: str | None):
+    if not val:
+        return None
+    try:
+        return float(val)
+    except Exception:
+        return None
+
+    if not val:
+        return None
+    dt = datetime.fromisoformat(val)
+    # make TZ-aware (assume local if naive; convert to UTC)
+    if dt.tzinfo is None:
+        dt = dt.replace(tzinfo=timezone.utc)
+    return dt
+
+def parse_dt(val: str | None) -> datetime | None:
+    if not val:
+        return None
+    dt = datetime.fromisoformat(val)
+    if dt.tzinfo is None:
+        dt = dt.replace(tzinfo=timezone.utc)
+    return dt
+