feat(topology): M2 - API-driven demo page with layout tables and dynamic rendering

- Add diagram_layouts and diagram_nodes tables
- Seed layout coordinates extracted from SVG
- Extend snapshot API to return layout data
- Rewrite demo page to fetch from API dynamically
- Support ?mission= and ?at= URL parameters
- Modal details populated from database component data
- Show/hide nodes based on component existence at snapshot time

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

topology_api/routes/snapshot.py

@@ -1,6 +1,8 @@
 # topology_api/routes/snapshot.py
 from flask import Blueprint, request, jsonify
-from topology_api.queries.snapshot_queries import resolve_snapshot_time, fetch_snapshot
+from topology_api.queries.snapshot_queries import (
+    resolve_snapshot_time, fetch_snapshot, fetch_layout,
+)
 
 snapshot_bp = Blueprint("snapshot", __name__)
 
@@ -47,6 +49,7 @@ def get_snapshot(base_code):
         })
 
     data = fetch_snapshot(snapshot_at)
+    layout = fetch_layout()
 
     return jsonify({
         "base": data["base"],
@@ -58,4 +61,5 @@ def get_snapshot(base_code):
         },
         "components": data["components"],
         "connections": data["connections"],
+        "layout": layout,
     })