Add value formatting to charts ($, %, units)

[ad4mou]

Summary

• Chart values can now show a currency symbol, %, or any unit (e.g. V, kg, GB) instead of bare numbers.
• Format is per series: a number format (d3-format) plus a unit placed before or after, so any currency or unit works, not a fixed list.
• Big numbers shorten sensibly: money/counts as K/M/B, scientific units (e.g. bytes) keep k/M/G.
• The admin Usage cost charts now show $.
• The chart editor lets you set the number format and a unit (with a Prefix/Suffix choice, clearable fields, and a link to the syntax docs).
• The value axis widens to fit long labels (e.g. $1,000,000) so they no longer clip.
• Formatting carries through into stories, including exported HTML (labels, KPI cards, tooltips).

Closes #1115

[github-actions]

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[cubic-dev-ai]

All reported issues were addressed across 15 files

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 3 files (changes from recent commits).

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[Bl3f]

small change

[Bl3f]

Here let's change the display, hide the row by default and only show it when clicked on a "format" icon that would be on the main row of the serie

[ad4mou]

Yes that's cleaner, Ok will do!