Add magnifying glass icon to remote-select inputs

[maebeale]

What is the goal of this PR and why is this important?

• Per Justin's comment on Change workshop dropdown on StoryIdea form #1506, a small UI tweak (in addition to the text changes in Clarify workshop search prompt on StoryIdea form #1509 / Update remote-select prompts to "Type to search …" #1527) would help users tell remote search fields apart from regular dropdowns
• Regular selects show a chevron caret on the right; remote-search fields had no distinguishing visual

How did you approach the change?

• Added a magnifying glass icon on the left of every remote-select field, injected by the existing Stimulus controller so all uses get it consistently
• Left placement (rather than right) creates a stronger structural distinction from the chevron-on-the-right selects nearby, and matches the convention from most search inputs (Google, GitHub, macOS)
• Wraps the Tom Select element in a .remote-select-container div the controller creates, so the icon positions against a container with predictable dimensions (positioning against .ts-wrapper directly was rendering clipped)
• Added left padding to the Tom Select control so typed text doesn't overlap the icon

UI Testing Checklist

• Visit a new StoryIdea form and confirm the workshop field shows a magnifying glass on the left
• Confirm the workshop field looks visually distinct from the Windows audience and Organization selects on either side
• Type into the workshop field and confirm typed text does not overlap the icon and the icon renders fully inside the rounded border
• Spot-check other remote-select fields (Story, WorkshopLog, WorkshopVariation, WorkshopVariationIdea, person/org affiliation fields, event registrations) — confirm the icon appears and search still works

Anything else to add?

• Affects all 8 views that use remote-select
• Companion to Clarify workshop search prompt on StoryIdea form #1509 (merged) and Update remote-select prompts to "Type to search …" #1527 (prompt-text changes for the remaining views)

[maebeale]

@jmilljr24 hope this was a good compromise! we're not doing the dropdown thing, but, doing a magnifying glass could help a lot w clarity. added a separate pr to update the prompt text for all of these.

[jmilljr24]

In my opinion its great. Hopefully this is enough to nudge them in the right direction.