feat(graph): metadata filters + facets (corpus graph PR A)

Adds legal-metadata filtering and the payload to color by it (foundation for
the color-by selector in the analytics PR).

Backend (web/graph_api.py, web/app.py) — read-only, G2:
- GraphNode += court, date (ISO) — precedents carry them for filter/color-by.
- build_corpus_graph += server-side WHERE filters (G5): court, precedent_level,
  chair, district, year_from, year_to (EXTRACT(YEAR FROM date)). Neighborhood
  query also selects court/date.
- New GET /api/graph/facets (response_model GraphFacets, UI2) → distinct
  courts/levels/chairs/districts so the UI doesn't hardcode Hebrew strings.

Frontend:
- graph.ts: GraphNode += court/date; GraphFilters += the six params;
  buildParams; useGraphFacets() hook.
- graph-filter-panel: an "advanced" Accordion with court/precedent_level/chair/
  district Selects (from facets) + year-from/year-to Selects.
- graph-view: new controls wired into filters; facets fetched and passed down.

Verified read-only against the live DB (precedent_level=עליון&year_from=2015
filters correctly; facets populated: 36 courts / 3 levels / 19 chairs / 4
districts). web-ui build + lint pass.

Invariants: G2 (SELECT-only via db.get_pool), G5 (filters server-side),
UI2 (explicit response_models). api:types to be regenerated post-deploy.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web-ui/src/components/graph/graph-view.tsx

@@ -13,6 +13,7 @@ import {
   type CorpusGraph,
   type GraphNode,
   useCorpusGraph,
+  useGraphFacets,
   useNodeNeighborhood,
 } from "@/lib/api/graph";
 import {
@@ -39,10 +40,17 @@ export function GraphView() {
     source: "",
     minCitations: 0,
     q: "",
+    court: "",
+    precedentLevel: "",
+    chair: "",
+    district: "",
+    yearFrom: 0,
+    yearTo: 0,
     showTopics: true,
     showPracticeAreas: true,
     showHalachot: false,
   });
+  const facets = useGraphFacets().data;
   const [selectedNode, setSelectedNode] = useState<GraphNode | null>(null);
   const [focusNodeId, setFocusNodeId] = useState<string | null>(null);
 
@@ -67,8 +75,26 @@ export function GraphView() {
       node_types: nodeTypes,
       limit: NODE_LIMIT,
       q: debouncedQ,
+      court: controls.court,
+      precedent_level: controls.precedentLevel,
+      chair: controls.chair,
+      district: controls.district,
+      year_from: controls.yearFrom,
+      year_to: controls.yearTo,
     }),
-    [controls.practiceArea, controls.source, controls.minCitations, nodeTypes, debouncedQ],
+    [
+      controls.practiceArea,
+      controls.source,
+      controls.minCitations,
+      controls.court,
+      controls.precedentLevel,
+      controls.chair,
+      controls.district,
+      controls.yearFrom,
+      controls.yearTo,
+      nodeTypes,
+      debouncedQ,
+    ],
   );
 
   const isFocused = !!focusNodeId;
@@ -106,7 +132,7 @@ export function GraphView() {
       </div>
 
       <div className="flex gap-4 h-[calc(100vh-320px)] min-h-[560px]">
-        <GraphFilterPanel controls={controls} onChange={onChange} />
+        <GraphFilterPanel controls={controls} onChange={onChange} facets={facets} />
 
         <div className="relative flex-1 rounded-lg border border-rule bg-surface overflow-hidden">
           {error ? (