Add historical sparklines to host cards

24h of snapshots were already being retained but never read. Adds a
windowed query (last ~40 samples/host, one query total via
ROW_NUMBER() OVER PARTITION BY, not N+1) embedded in the existing
/api/hosts response, rendered as small hand-rolled SVG sparklines
(cpu/mem/disk overlaid) -- no charting library needed at this scale.

Closes #10.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/api/src/routes/hosts.ts

@@ -1,6 +1,6 @@
 import type { FastifyInstance, FastifyReply, FastifyRequest } from "fastify";
 import type Database from "better-sqlite3";
-import { getLatestSnapshots } from "../db/index.js";
+import { getLatestSnapshots, getRecentHistory } from "../db/index.js";
 
 async function requireAuth(req: FastifyRequest, reply: FastifyReply) {
   if (!req.session.username) {
@@ -11,6 +11,13 @@ async function requireAuth(req: FastifyRequest, reply: FastifyReply) {
 export function registerHostRoutes(app: FastifyInstance, db: Database.Database): void {
   app.get("/api/hosts", { preHandler: requireAuth }, async () => {
     const rows = getLatestSnapshots(db);
+
+    const history = new Map<string, { ts: string; cpuPct: number | null; memPct: number | null; diskPct: number | null }[]>();
+    for (const h of getRecentHistory(db)) {
+      if (!history.has(h.host_id)) history.set(h.host_id, []);
+      history.get(h.host_id)!.push({ ts: h.ts, cpuPct: h.cpu_pct, memPct: h.mem_pct, diskPct: h.disk_pct });
+    }
+
     return {
       hosts: rows.map((r) => ({
         hostId: r.host_id,
@@ -24,6 +31,7 @@ export function registerHostRoutes(app: FastifyInstance, db: Database.Database):
         cpuPressurePct: r.cpu_pressure_pct,
         uptimeSec: r.uptime_sec,
         lastSeen: r.ts,
+        history: history.get(r.host_id) ?? [],
       })),
     };
   });