perf: scope filter animation to mutation site, cache per-table filters

[datlechin]

Summary

• Moved filter panel animation from parent .animation() to withAnimation at mutation site — .animation(value: filterStateManager.isVisible) on the results section parent caused SwiftUI to re-evaluate the entire view tree 12+ times per frame during the 0.2s transition. Now withAnimation is called inside toggle()/show()/close() on FilterStateManager, scoping the animation to only the filter panel transition.
• Removed .animation(value: tab.errorMessage) — error banners should appear instantly, no need for animation on the entire results section.
• Added per-table filter cache to FilterSettingsStorage — loadLastFilters(for:) was decoding JSON from UserDefaults on every table switch. Now cached in memory, invalidated on save/clear.

Test plan

• Toggle filter panel — verify smooth slide animation still works
• Trigger a query error — verify error banner appears instantly (no animation delay)
• Switch between tables — verify filters load correctly (cached after first load)
• Save filters on table A, switch to B, switch back to A — verify A's filters are preserved
• Clear filters — verify cache is invalidated