Highlight active bottom tab bar section with PyCon 2026 pink

[JacobCoffee]

Summary

• Ionic's built-in tab-selected detection wasn't firing for any tab in this app, so every tab button always read as inactive regardless of which section you were in.
• Drive the active tab explicitly from the router URL (first path segment under `/app/tabs/`) and apply a `pycon-active` class to the matching `ion-tab-button`.
• Active tab uses `--color: #DD04D2` (PyCon 2026 neon pink) with a bold label.

Test plan

• Open Schedule — Schedule tab is pink + bold; others are default gray
• Open Speakers — Speakers tab is pink; others default
• Open Map (Conference Center) — Map tab is pink
• Open Now — Now tab is pink
• Logged out → open Login — Login tab is pink
• Navigate between tabs — highlight moves in real time (no stale highlight)
• Side-menu-only pages (About PyCon, COC, Wifi, etc.) — no tab highlighted, same as before

[JacobCoffee]