feat: add dark mode support to stop marker popup and fix related dark mode issues

[sannidhyaroy]

Summary

• Add dark mode support to PopupContent.svelte (stop marker popup) [closes Add dark mode support to PopupContent.svelte (stop popup) #443]
• Add dark mode overrides for Leaflet popup wrapper and tip (.leaflet-popup-content-wrapper, .leaflet-popup-tip)
• Fix close button hover in ModalPane showing white background in dark mode
• Add dark mode text color to "Route Schedules" heading on the schedule page

Screenshots

PopupContent (stop popup)

Before	After

Leaflet popup wrapper (impacts both stop popup and vehicle popup)

Before	After

ModalPane close button hover

Before	After

Route Schedules heading

Before	After

Additional Questions

The stop popup currently shows Arrival time: inside a purple badge. Since the badge already visually separates it from the time value, should the trailing colon be removed (i.e. just Arrival time)? I left it unchanged for now.

Test plan

• Toggle dark mode and click a stop marker on a route map. Popup should have dark background with readable text
• Verify Leaflet popup wrapper matches the dark background (no white border)
• Hover over the close (X) button on any sidebar pane in dark mode and it should show subtle dark highlight, not white
• Navigate to a stop's schedule page in dark mode and the "Route Schedules" heading should be readable
• Verify all above still look correct in light mode
• npm run lint passes

[CLAassistant]

All committers have signed the CLA.

[Copilot]

Pull request overview

Adds/finishes dark-mode styling for stop marker popups and a few related UI elements to ensure consistent readability and remove light-theme artifacts when the app is in dark mode.

Changes:

• Added dark: Tailwind classes to PopupContent.svelte (stop marker popup).
• Added dark-mode CSS overrides for Leaflet popup wrapper/tip and adjusted modal close-button hover styling.
• Fixed dark-mode text color for the “Route Schedules” heading.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/routes/stops/[stopID]/schedule/+page.svelte	Adds dark-mode text color to the page heading for readability.
src/components/navigation/ModalPane.svelte	Removes component-scoped close-button styling (moved global), leaving an empty style block.
src/components/map/PopupContent.svelte	Adds dark-mode background/text classes to the stop popup content.
src/assets/styles/leaflet-map.css	Adds .dark overrides for Leaflet popup wrapper/tip to prevent light borders/background.
src/app.css	Centralizes .close-button styling and fixes dark-mode hover background color.

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[sannidhyaroy]

Dropped the trailing colon from the "Arrival time" label as confirmed by @tarunsinghofficial in our Slack discussion.