Better channels UI (more channels by default)

[pskillen]

Parent epic: pskillen/meshflow-api#341

Type: enhancement | Area: Channels / constellations

Problem

Channel lists are hard to scan as deployments grow (more MC channels). Current view may truncate or require too many clicks.

Proposal

• Search/filter; table or card grid with mc_channel_idx, protocol, constellation.
• Collapse by constellation; surface MC sync/apply status where API supports it.

Acceptance criteria

• Find channel by name without unbounded dropdown scroll.
• 10+ MC channels usable on desktop/tablet.