docs: update CONTEXT.md for v0.5.0 session

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

CONTEXT.md

@@ -7,7 +7,7 @@
 >
 > Ask Claude Code: "Please update CONTEXT.md with what we did today"
 
-Last updated: 2026-02-16 (session 14)
+Last updated: 2026-02-16 (session 15)
 
 ---
 
@@ -22,15 +22,31 @@ Last updated: 2026-02-16 (session 14)
 ## Current project state
 
 ### felhom-controller (this repo)
-- **Version:** v0.4.7
+- **Version:** v0.5.0
 - **Phase 1:** ✅ COMPLETE — Stack Manager + Deploy Flow
 - **Phase 2:** ✅ COMPLETE — Monitoring & Health (scheduler, CPU/temp, healthchecks.io pings)
 - **Phase 3:** ✅ COMPLETE — Backups (DB dumps, restic integration, manual trigger, **dedicated backup page**)
+- **Phase 4:** ✅ COMPLETE — Monitoring Page with Metrics Store (SQLite, Chart.js, system + container metrics)
 - **First app deployed:** Paperless-ngx on demo-felhom.eu (2026-02-13)
 - **Running on:** demo-felhom (N100 mini PC) at 192.168.0.162:8080
-- **All Phase 1-3 features working:** deploy, start/stop/restart/update, logs, health-aware states, auth, monitoring, backups, backup detail page
+- **All Phase 1-4 features working:** deploy, start/stop/restart/update, logs, health-aware states, auth, monitoring, backups, backup detail page, system monitoring page
 
-### What was just completed (2026-02-16 session 14)
+### What was just completed (2026-02-16 session 15)
+- **v0.5.0 — Backup Bugfixes + Monitoring Page with Metrics Store:**
+  - **Task 1: Fixed "Helyi mentés" showing "–" after restart** — `GetFullStatus()` now synthesizes `LastBackup` from `SnapshotHistory` and `LastDBDump` from `DumpFiles` on disk when the in-memory values are nil (e.g., after controller restart). Dashboard handler also updated to use `GetFullStatus()` instead of `GetStatus()` for consistent behavior.
+  - **Task 2: Verified backup page caching** — Already implemented in v0.4.7 (`RefreshCache`, scheduler job, `AfterBackup` callback). No changes needed.
+  - **Task 3: New Monitoring Page ("Rendszermonitor")** — Full system monitoring subsystem:
+    - **SQLite metrics store** (`internal/metrics/store.go`, `types.go`): WAL-mode SQLite via `modernc.org/sqlite` (pure Go, no CGO). Stores system metrics (CPU%, memory, temperature, load) and container metrics (CPU%, memory, net/block I/O) with timestamp. Downsampled queries via bucket-based `GROUP BY` for Chart.js. 30-day auto-prune via daily scheduler job at 04:00.
+    - **Metrics collector** (`internal/metrics/collector.go`): Background goroutine collects system + container metrics every 60 seconds. System data from `system.GetInfo()`, container data from `docker stats --no-stream` with tab-separated format parsing.
+    - **System info provider** (`internal/metrics/sysinfo.go`, `sysinfo_other.go`): Reads hostname, OS, kernel, CPU model/cores, uptime from `/proc` filesystem. Linux-specific with build-tag fallback for cross-compilation.
+    - **REST API endpoints** (4 new routes in `router.go`): `GET /api/metrics/system` (time-series with range presets), `GET /api/metrics/containers/summary` (current stats), `GET /api/metrics/containers/{name}` (per-container time-series), `GET /api/metrics/sysinfo` (static system info).
+    - **Monitoring page template** (`monitoring.html`): 5 sections — System Overview (sysinfo via API), System Metrics Charts (4 line charts: CPU, Memory, Temperature, Load in 2×2 grid), Container Resources (2 horizontal bar charts: CPU% and Memory), Per-container Detail (click to expand with historical charts), Storage (server-rendered progress bars). Time range selectors (1h/6h/24h/7d/30d). Auto-refresh every 60s.
+    - **Chart.js 4.4.7** embedded locally (offline environments, ~200KB UMD), dark theme configuration matching site design.
+    - **CSS**: ~100 lines added for monitoring page (`.monitor-card`, `.charts-grid`, `.chart-box`, `.container-charts-row`, `.storage-bars`, responsive rules).
+    - **Wiring**: 4th sidebar nav item "Rendszermonitor", metrics DB path in named volume (`data/metrics.db`), `/etc/os-release:/host/etc/os-release:ro` volume mount in docker-compose.yml, Dockerfile updated to `golang:1.24-bookworm` (required by `modernc.org/sqlite`), `go.mod` upgraded to `go 1.24.0`.
+  - **Controller version:** v0.5.0 — deployed and verified on demo-felhom.eu (metrics collecting, 16 containers reporting, sysinfo showing Intel N100 correctly)
+
+### What was previously completed (2026-02-16 session 14)
 - **v0.4.7 — Protected Stack Detail Pages + Backup Page Caching:**
   - **Protected stacks clickable** — `data-href` gating changed from `{{if not .Protected}}` to `{{if .Meta.Slug}}` on both `stacks.html` and `dashboard.html`. Protected stacks with `.felhom.yml` (i.e. a slug) are now clickable, linking to `/apps/{slug}`. Stacks without `.felhom.yml` remain non-clickable.
   - **"Részletek" button for protected stacks** — Protected stack action section in `stacks.html` now shows a "Részletek" link when the stack has a slug, next to the restart button.
@@ -344,6 +360,11 @@ Last updated: 2026-02-16 (session 14)
 | Restic password auto-generated | No manual setup needed — generated on first backup run, stored in named volume |
 | DB discovery via docker inspect | No config needed — discovers postgres/mariadb containers by image name + env vars |
 | Backup orchestrator with running flag | Prevents concurrent backups, supports both scheduled and manual trigger |
+| modernc.org/sqlite (pure Go) | No CGO/gcc needed in Docker build stage — keeps `CGO_ENABLED=0` static binary |
+| Chart.js embedded locally | Customer hardware may not have internet — CDN not reliable for offline environments |
+| Metrics downsampling via SQL | Bucket-based AVG in GROUP BY keeps Chart.js responsive with up to 30 days of data |
+| 60s metrics collection interval | Good balance of resolution vs. storage — ~44K rows/month for system metrics |
+| /etc/os-release mounted read-only | Container can't read host OS info directly — mount to /host/etc/os-release:ro |
 
 ## Key file locations on demo-felhom