feat: add plagiarism graph, domain API services, error/empty-state handling, and UI polish

- Add PlagiarismGraphComponent (force-graph) with legend, abbreviated names,
  risk-derived node colors, and particle animation; integrated into work, event,
  group, and student detail pages
- Extract domain API services (students, events, groups, reference-sets, users,
  analysis-runs, audit) from WorksApiService
- Add RiskLevelPipe for translating risk level values to Russian
- Replace raw IDs with entity names across all detail page overview sections
- Dashboard: remove Works tab, reorder tabs (Students, Events, Groups, Ref-sets),
  hide list cards when empty or on error
- Hide secondary blocks (runs, matches, graph, analytics) on error instead of
  showing error text; keep top-level entity load errors visible
- Refset detail: split Ingestions tab into separate list and upload cards;
  hide list card when empty or on error
- Convert analysis runs list to table; fix kv-grid vertical alignment
- Style native select[tuiSelect] to match other form fields
- Add favicon (yellow star) from sparkguardian
- Add CLAUDE.md, .env.example, proxy config, CI workflow, and Makefile

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

proxy.conf.cjs

@@ -0,0 +1,15 @@
+/**
+ * Прокси для `ng serve`. Целевой backend задаётся в `.env` (SG_DEV_PROXY_TARGET).
+ */
+const path = require('path');
+require('dotenv').config({ path: path.join(__dirname, '.env') });
+
+const target = process.env.SG_DEV_PROXY_TARGET || 'http://spark.returntozer0.ru';
+
+module.exports = {
+  '/api/**': {
+    target,
+    secure: false,
+    changeOrigin: true,
+  },
+};