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/migrations/004_layout.sql

@@ -0,0 +1,34 @@
+-- topology_api/migrations/004_layout.sql
+-- Diagram layout tables for topology visualization
+
+CREATE TABLE topology.diagram_layouts (
+    id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+    base_id uuid NOT NULL REFERENCES topology.bases(id),
+    layout_key text NOT NULL,
+    name text NOT NULL,
+    canvas_width numeric NOT NULL DEFAULT 1500,
+    canvas_height numeric NOT NULL DEFAULT 1900,
+    is_default boolean NOT NULL DEFAULT false,
+    created_at timestamptz NOT NULL DEFAULT now(),
+    CONSTRAINT uq_layout_base_key UNIQUE (base_id, layout_key)
+);
+
+CREATE TABLE topology.diagram_nodes (
+    id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+    layout_id uuid NOT NULL REFERENCES topology.diagram_layouts(id),
+    component_id uuid REFERENCES topology.components(id),
+    node_key text NOT NULL,
+    x numeric NOT NULL,
+    y numeric NOT NULL,
+    width numeric NOT NULL DEFAULT 200,
+    height numeric NOT NULL DEFAULT 120,
+    rotation_deg numeric NOT NULL DEFAULT 0,
+    style_key text NOT NULL DEFAULT 'node-card',
+    label_override text,
+    z_index integer NOT NULL DEFAULT 0,
+    created_at timestamptz NOT NULL DEFAULT now(),
+    CONSTRAINT uq_diagram_node UNIQUE (layout_id, node_key)
+);
+
+CREATE INDEX IF NOT EXISTS idx_diagram_nodes_layout
+    ON topology.diagram_nodes(layout_id);