feat(android): add optional floating bottom navigation bar

[qpst4]

Summary

Adds an optional floating glass-style bottom navigation bar on Android (enabled by default in theme settings). When enabled, the nav bar renders as a frosted capsule above page content instead of a full-width docked bar.

Also improves the active tab indicator alignment so the selected pill sits flush with the capsule edges on the first and last tabs.

Changes

• Floating nav bar UI: blur backdrop, rounded capsule, shadow, and safe-area spacing
• Theme setting: new toggle useFloatingNavBar under Theme (with i18n for en / ru / zh-CN / zh-TC)
• Layout integration: scroll padding and FAB position adjust when floating mode is active; disabled on Android TV
• Active tab fit: full-width nav layout, spaceBetween alignment, tuned padding and border radius
• Localization: regenerate l10n for new strings; remove invalid generic zh locale entry that broke builds

Test plan

• Android phone: enable Theme → Floating navigation bar, verify capsule bar floats above content
• Switch tabs (first / middle / last): active pill aligns with capsule left/right edges
• Disable floating nav bar: classic full-width bottom bar still works
• Dashboard / Proxies / Profiles / Tools: content is not obscured (scroll padding)
• Android TV: floating bar is not used
• Haptic feedback on tab switch still works when enabled

[appshubcc]

The floating bottom navigation feels a bit out of place with the current UI