dashboard: pace a querying chart by its window, and an example to evaluate it

A chart is drawn in buckets, and nothing it can show changes until the
bucket it is drawing closes — so the resolution sets the refresh rather
than a flat five-second floor. A week at quarter-hour buckets now asks
four times an hour instead of sixty, for the same picture. Leaving the
field empty follows the window; a slower rate is still honoured.

`make seed-example` builds the thing to evaluate it with: a flow that
logs a temperature to InfluxDB, a flow that answers a chart's request by
turning the window into Flux and the rows back into a series, and a
dashboard holding the chart. The reading flow declares the request as an
input with a starting value, which is how a flow says a value reaches it
from a panel rather than from a node upstream.

Axis labels keep enough decimals to stay distinct — `si` rounds to three
figures, so every tick of a chart living inside one degree read "19".

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

NOTEPAD.md

@@ -13,6 +13,8 @@ should reopen it.
 
 ### To be sorted
 
+- BUG/UI when a dashboard widget is selectd, the border does not cleanly draw on the left side of the widget
+- BUG/UI there is currently no option to discard changes (in dashboard or flow viewport); we should make add a "X" button to discard and replace "Publish" by the already existing checkmark button which is either clickable when there are unpublished changes or unclickable when the changes have been applied (but the icon stays). The discard button should only show when there are changes (hidden else)
 - INFRA: ensure that all the packages/ dependencies needed to run fluksio are available on arm to make this software runnable on e.g. raspbian
 - INFRA: merge the philosophy statement at the beginning of vision.md into the rest of the document. Dissolve the decision dates and fold the decisions into a clean structure
 - BUG/UI mobile friendly support is degraded: 1) toolbar in the "Flows" viewport extend mobile viewport width 2) position of nodes should never be static (holds true for desktop as well); always adjust such that there are as few as possible overlaps (of nodes and edge labels) and direction is left to right (desktop) or top to bottom (mobile) with a minimal (but clean) overall edge length. This should also remove the ability to drag nodes around; their position is fixed by an algorithm. This design choice is what enforces small atomic flows (different from nodered) 3) Dashboard view is not mobile friendly at all; as dashboard design is infeasible on mobile, render all widgets in a vertically stacked order. This allows to inspect each widget and make changes. Layout changes are not a feature on mobile 4) the home view is not responsive; all items shown there should re-order on mobile such that no scrollbars appear. Make sure the mobile support is anchored in the design such that future work does not break it
@@ -110,6 +112,7 @@ Decisions taken up front, because most items below depend on them:
   an InfluxDB node behind a build/parse pair, with the panel's own range picker
   governing the window. The pieces are in and verified against a real bucket;
   what is missing is a dashboard someone would actually hang.
+- CHORE/UI: `MarkdownWidget`'s docstring claims "headings, bold, code, links, list items"; only headings and bullets are implemented. Either the inline spans or the docstring.
 - CHORE/UI: identical in-flight chart requests are deduplicated per browser tab,
   so two wall panels showing the same tile still run the query twice. An
   `interval` on the request port is the backstop, and it belongs to the flow