Add Web-Dashboard page (Unit 12)

Covers decnet web / serve-web, env vars, admin credential enforcement,
pages (Dashboard, DeckyFleet, LiveLogs, Attackers, AttackerDetail,
Config, Bounty), JWT auth flow, must_change_password, server-side UI
gating, client build, and CORS defaults.

Web-Dashboard.md

@@ -0,0 +1,158 @@
+# Web Dashboard
+
+The DECNET Web Dashboard is a React + TypeScript + Vite single-page app that
+talks to the FastAPI backend exposed by the DECNET API server. It is the
+operator-facing control surface for inspecting deckies, attackers, live logs,
+bounties, and runtime configuration.
+
+Related:
+[REST API](REST-API-Reference) -
+[Environment variables](Environment-Variables) -
+[Security & stealth](Security-and-Stealth).
+
+## Running
+
+Two processes are involved: the API server (FastAPI) and the web front-end
+(static SPA with a thin `/api/*` reverse proxy).
+
+```bash
+# Start the FastAPI backend (serves the REST API on DECNET_API_PORT).
+decnet serve-api
+
+# Serve the Web Dashboard (static SPA).
+decnet web \
+    --host 0.0.0.0 \
+    --web-port 8080 \
+    --api-port 8000
+```
+
+`decnet web` loads the pre-built bundle from `decnet_web/dist/` and refuses to
+start if that directory is missing. The handler proxies any request whose path
+starts with `/api/` to the backend on `--api-port`, so the SPA can use relative
+URLs and no CORS round-trip is needed in the default topology. Add `--daemon`
+to detach into the background.
+
+### Environment variables
+
+| Variable | Default | Purpose |
+|---|---|---|
+| `DECNET_WEB_HOST` | `127.0.0.1` | Bind address for the SPA server. |
+| `DECNET_WEB_PORT` | `8080` | Port for the SPA server. |
+| `DECNET_ADMIN_USER` | `admin` | Admin username seeded on first boot. |
+| `DECNET_ADMIN_PASSWORD` | `admin` | Admin password seeded on first boot. |
+| `DECNET_JWT_SECRET` | required | HS256 signing secret, must be at least 32 characters. |
+| `DECNET_CORS_ORIGINS` | `http://<web_host>:<web_port>` | Comma-separated allowlist for backend CORS. |
+
+The CORS default resolves wildcard bind addresses (`0.0.0.0`, `::`) to
+`localhost` when building the default origin. Override with something like:
+
+```
+DECNET_CORS_ORIGINS=http://192.168.1.50:9090,https://dashboard.example.com
+```
+
+### Admin credentials
+
+The literal pair `admin` / `admin` is a known-bad default. The web layer
+refuses to start with those values outside pytest: set **both**
+`DECNET_ADMIN_USER` and `DECNET_ADMIN_PASSWORD` to non-default values before
+running `decnet web` or `decnet serve-api` in production. See the admin
+credentials section in [Environment variables](Environment-Variables) for the
+exact enforcement rules.
+
+On first boot the admin record is seeded with `must_change_password=True`, and
+the frontend forces a password change on the next login.
+
+## Pages
+
+The routes are defined in `decnet_web/src/App.tsx`. All pages share the
+`Layout` chrome (top bar with search + logout, left nav).
+
+- **Dashboard** (`/`, `Dashboard.tsx`) - Landing view. Summary tiles for decky
+  count, attacker count, recent log volume, and top-level activity charts. The
+  top-bar search box is threaded in as `searchQuery` so the dashboard can
+  filter its recent-events pane inline.
+- **DeckyFleet** (`/fleet`, `DeckyFleet.tsx`) - Fleet control panel. Lists
+  every decky with status, IP, services, and mutation interval. Admin-only
+  controls let you redeploy from an INI payload, mutate or kill individual
+  deckies, and retune mutation intervals. Backed by the `fleet/` router group.
+- **LiveLogs** (`/live-logs`, `LiveLogs.tsx`) - Streaming log tail across the
+  whole fleet. Events are parsed with `utils/parseEventBody.ts` to pull out
+  attacker IP, decky, service, and RFC 5424 structured data fields. An
+  artifact drawer (`ArtifactDrawer.tsx`) pops open when a log line references
+  an uploaded payload.
+- **Attackers** (`/attackers`, `Attackers.tsx`) - Grouped view of observed
+  source IPs with hit counts, first/last seen, and targeted services. Click
+  through to the detail page.
+- **AttackerDetail** (`/attackers/:id`, `AttackerDetail.tsx`) - Full
+  per-attacker timeline: every log line tied to that IP, captured credentials
+  and commands, any uploaded artifacts, and bounty status if applicable.
+- **Config** (`/config`, `Config.tsx`) - Runtime configuration and user
+  management. Admins can view and edit the running INI config, reinitialize
+  the fleet, and create, update, or delete dashboard users. Non-admins cannot
+  reach this page; see "Server-side UI gating" below.
+- **Bounty** (`/bounty`, `Bounty.tsx`) - Displays bounty offers and redemption
+  state attached to particular attacker behaviors. Read-only view over the
+  `bounty/` router group.
+
+## Authentication
+
+The backend exposes `POST /auth/login` (see
+`decnet/web/router/auth/api_login.py`). The handler loads the user via a
+cached lookup, verifies the password with bcrypt off the event loop, and
+returns a `Token` payload:
+
+```json
+{
+  "access_token": "<JWT>",
+  "token_type": "bearer",
+  "must_change_password": false
+}
+```
+
+JWT details (`decnet/web/auth.py`):
+
+- Algorithm: **HS256**.
+- Secret: `DECNET_JWT_SECRET` (must be at least 32 characters; short or
+  known-bad values abort startup).
+- Lifetime: **1440 minutes** (24 hours).
+- Claims: `uuid` (user UUID), `iat`, `exp`.
+
+The SPA stores the token in `localStorage` and decodes the `exp` claim on
+boot to decide whether to show the login screen (`App.tsx`).
+
+### must_change_password flow
+
+When the login response carries `must_change_password: true` the SPA forces a
+password-change dialog before any other page loads. Internally, the FastAPI
+dependency `get_current_active_user` returns HTTP 403 for any protected route
+while the flag is set, so the rest of the API is effectively gated until the
+user calls `POST /auth/change-password`, which clears the flag via
+`repo.update_user_password(..., must_change_password=False)`.
+
+## Server-side UI gating
+
+**Admin-only UI must be gated by the backend, not by client-side role
+checks.** Every mutating or privileged endpoint under the `fleet/`, `config/`,
+and `artifacts/` router groups is protected by the `require_admin` FastAPI
+dependency (`decnet/web/dependencies.py`). The SPA may hide or disable admin
+controls for UX, but that is a presentation convenience only - a non-admin
+user who hand-crafts requests still gets HTTP 403 from the server. Do not
+introduce features whose only access check is `if user.role === 'admin'` in
+React; that check must exist on the server side as well.
+
+## Client build
+
+The front-end lives in `decnet_web/` and is a standard Vite project.
+
+```bash
+cd decnet_web
+npm install
+npm run build        # production bundle -> decnet_web/dist/
+npm run dev          # hot-reload dev server (proxies /api/* to the backend)
+```
+
+`decnet web` expects the production bundle at `decnet_web/dist/` relative to
+the installed package (`Path(__file__).parent.parent / "decnet_web" / "dist"`
+in `decnet/cli.py`). If you are working on the SPA, rebuild before running
+`decnet web`, or use `npm run dev` and point your browser at the Vite dev
+server during development.