Add homelab dashboards: system, LLM, and UPS on one domain

Three dashboards served by one FastAPI app with a SQLite history store
(raw / 1m / 1h) and hand-written SVG charts: no Prometheus, no Grafana,
no CDN, no build step. Nothing is fetched from the internet at runtime.

* system: a stdlib-only agent (agent/host_agent.py) reports /proc and
  /sys counters; the dashboard turns them into rates over a labelled
  window, so every number says how it was measured.
* llm: gufo/llama.cpp and vLLM /metrics are parsed by an in-house
  exposition parser. Measured delta/elapsed throughput beats a native
  per-request gauge, and each value carries its provenance.
* ups: a NUT wire-protocol client plus health checks that name what
  they looked at. Commands are gated by NUT_ALLOW_ACTIONS,
  DASH_READ_ONLY and a DANGER confirmation, re-checked server-side.

Missing values render as n/a rather than 0, and an unconfigured source
answers 404 {"configured": false} without dialling anything, so "not
deployed here" never looks like an outage.

253 tests at 94% coverage against captured real fixtures; ruff and
pyright clean.

LLM-Generated: true

tests/fixtures/metrics_gufo.txt

@@ -0,0 +1,45 @@
+# HELP gufo_device_lost_total Confirmed GPU context losses
+# TYPE gufo_device_lost_total counter
+gufo_device_lost_total 0
+# HELP llamacpp:prompt_tokens_total Total prompt tokens processed, excluding cache hits
+# TYPE llamacpp:prompt_tokens_total counter
+llamacpp:prompt_tokens_total 1350666
+# HELP llamacpp:prompt_tokens_cached_total Total prompt tokens reused from cache
+# TYPE llamacpp:prompt_tokens_cached_total counter
+llamacpp:prompt_tokens_cached_total 124529105
+# HELP llamacpp:prompt_seconds_total Prompt process time
+# TYPE llamacpp:prompt_seconds_total counter
+llamacpp:prompt_seconds_total 1478.1443332270005
+# HELP llamacpp:tokens_predicted_total Total tokens generated
+# TYPE llamacpp:tokens_predicted_total counter
+llamacpp:tokens_predicted_total 877336
+# HELP llamacpp:tokens_predicted_seconds_total Predict process time
+# TYPE llamacpp:tokens_predicted_seconds_total counter
+llamacpp:tokens_predicted_seconds_total 26565.247833160014
+# HELP llamacpp:n_tokens_max Largest observed n_tokens.
+# TYPE llamacpp:n_tokens_max counter
+llamacpp:n_tokens_max 252622
+# HELP llamacpp:spec_decode_num_drafts_total Total speculative verification rounds
+# TYPE llamacpp:spec_decode_num_drafts_total counter
+llamacpp:spec_decode_num_drafts_total 291738
+# HELP llamacpp:spec_decode_num_draft_tokens_total Total draft tokens proposed
+# TYPE llamacpp:spec_decode_num_draft_tokens_total counter
+llamacpp:spec_decode_num_draft_tokens_total 789028
+# HELP llamacpp:spec_decode_num_accepted_tokens_total Total draft tokens accepted
+# TYPE llamacpp:spec_decode_num_accepted_tokens_total counter
+llamacpp:spec_decode_num_accepted_tokens_total 578514
+# HELP llamacpp:prompt_tokens_seconds Prompt processing speed in tokens per second
+# TYPE llamacpp:prompt_tokens_seconds gauge
+llamacpp:prompt_tokens_seconds 160.47362399350274
+# HELP llamacpp:predicted_tokens_seconds Generation speed in tokens per second
+# TYPE llamacpp:predicted_tokens_seconds gauge
+llamacpp:predicted_tokens_seconds 42.621031668072597
+# HELP llamacpp:requests_processing Number of admitted requests, including cache preparation
+# TYPE llamacpp:requests_processing gauge
+llamacpp:requests_processing 0
+# HELP llamacpp:requests_deferred Number of requests waiting for a session
+# TYPE llamacpp:requests_deferred gauge
+llamacpp:requests_deferred 0
+# HELP llamacpp:kv_cache_usage_ratio In-flight prompt and generated tokens over sessions times context; excludes retained cache
+# TYPE llamacpp:kv_cache_usage_ratio gauge
+llamacpp:kv_cache_usage_ratio 0