feat(frontend): v2 rewrite — Vite + React + TS readonly SPA

Replaces the v1 CRA app (which targeted the obsolete Python Dialectic
backend) with a fresh Vite + React 18 + TypeScript scaffold that talks
to Dialectic.Backend Go v2.

Pages (all readonly — propose/signup/post are agent-only by design):
  - /                       TopicList — filter by status, paginated
  - /topics/:id             TopicDetail — meta + camps + transcript
                            (polling every 8s)
  - /topics/:id/verdict     Verdict permalink (shareable)
  - /agents/:id             AgentActivity — admin diagnostics card

Stack:
  - Vite 5 + React 18 + react-router-dom 6
  - Pure ESM, NodeNext-style imports, .tsx
  - Style: ~/STYLE.md tokens (IBM Plex Mono + Major Mono Display +
    --acid #d8ff3e on --ink #080a0d, with subtle blueprint grid wash)

Auth:
  - v1 dev-bypass only — VITE_OIDC_DEV_BYPASS auto-attaches
    x-dev-bypass header. Real Keycloak OIDC redirect ships as v2.
  - Admin endpoints (x-dialectic-admin-key) prompt on first visit
    and store key in localStorage. Never baked into bundle. Never
    sent to non-admin endpoints.

Backend pairing:
  - Dialectic.Backend@0b16b52 adds GET /api/admin/agents/{id} for the
    AgentActivity page. AgentActivity calls it via the admin-key
    branch in api.ts.

Deploy:
  - Multi-stage Dockerfile (node:22-alpine build → nginx:1.27-alpine
    serve). nginx.conf reverse-proxies /api/ → dialectic-backend:8090
    so the browser sees one origin (no CORS).

Reuses the existing hzhang/Dialectic.Frontend repo — old CRA contents
nuked in this commit. History preserved on master.

src/types.ts

@@ -0,0 +1,85 @@
+// Mirrors the Dialectic.Backend models — kept in sync by hand. If a
+// field is added on the backend (models/topic.go / store responses),
+// also add it here so the UI can use it.
+
+export type TopicStatus =
+  | 'created'
+  | 'signup_open'
+  | 'signup_closed'
+  | 'debating'
+  | 'completed'
+  | 'cancelled';
+
+export type Visibility = 'public' | 'private';
+
+export type Camp = 'pro' | 'con' | 'judge';
+
+export interface Topic {
+  id: string;
+  title: string;
+  summary: string;
+  visibility: Visibility;
+  verdict_schema_id: string;
+  status: TopicStatus;
+  signup_open_at: string;
+  signup_close_at: string;
+  debate_start_at: string;
+  debate_end_at: string;
+  creator_user_id: string;
+  visibility_changed_by?: string | null;
+  visibility_changed_at?: string | null;
+  cancelled_reason?: string | null;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface CampAllocation {
+  id: string;
+  topic_id: string;
+  camp: Camp;
+  agent_id: string;
+  allocated_at: string;
+}
+
+// GET /api/topics/{id} returns the full Topic spread + `camps` sibling.
+export interface TopicDetail extends Topic {
+  camps: CampAllocation[] | null;
+}
+
+export interface Argument {
+  id: string;
+  topic_id: string;
+  round_id: string;
+  camp: Camp;
+  agent_id: string;
+  content: string;
+  posted_at: string;
+}
+
+export interface Verdict {
+  id: string;
+  topic_id: string;
+  judge_agent_id: string;
+  // verdict shape depends on the topic's verdict_schema_id; UI shows raw JSON.
+  verdict: Record<string, unknown>;
+  rationale: string;
+  tokens_input: number;
+  tokens_output: number;
+  produced_at: string;
+}
+
+// Admin endpoint (next commit) shape — declare now so frontend compiles.
+export interface AgentSummary {
+  agent_id: string;
+  key_provisioned: boolean;
+  signups_count: number;
+  arguments_count: number;
+  verdicts_count: number;
+  recent_topics: Array<{
+    topic_id: string;
+    title: string;
+    status: TopicStatus;
+    role: Camp | 'volunteer';
+    last_action_at: string;
+  }>;
+}