Fix remote local timeline filter switching from sidebar

[Dimillian]

Motivation

• Selecting a remote-local timeline from the sidebar could not be switched to local/federated/trending using the toolbar menu because the tab was created with a constant TimelineFilter binding.
• The toolbar menu expects a mutable binding so changes propagate to the displayed timeline view for that sidebar tab.
• The intent is to keep per-sidebar-tab filter stateful so toolbar filter actions apply when a remote-local timeline tab is opened.

Description

• Replace the direct use of TimelineTab(timeline: .constant(filter)) for .anyTimelineFilter with a small wrapper view TimelineFilterTab that owns a @State private var timeline initialized with the provided filter.
• TimelineFilterTab exposes a binding to the internal timeline and forwards it to TimelineTab via TimelineTab(timeline: $timeline) so toolbar changes mutate the tab state.
• Change is contained in IceCubesApp/App/Tabs/Tabs.swift and adds the private TimelineFilterTab struct.

Testing

• No automated tests were run as part of this change.
• No CI build or test results are available for this PR.

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Codex Task