New default antenna widget icons sbc changes

[DmtryJS]

OSD Configuration Optimization for SBC Ground Station

Summary

This PR optimizes the PixelPilot OSD configuration (osd.json) for better screen real estate usage, improved signal granularity, and enhanced readability on SBC ground stations.

Changes Made

Icon Resolution Optimization
Before: 96×96px signal icons (too large, causing overflow)
After: 24×24px signal icons (matches other widget icons)
Benefit: Icons fit properly within screen bounds without clipping

RSSI Signal Granularity
Before: 5 signal levels
After: 8 signal levels
Benefit: More precise signal strength visualization for better link quality assessment

Antenna Icon Layout
Evenly distributed 6 antenna icons across the row
X coordinates: -250 to -80 (34px spacing between icons)
Alignment: First antenna icon aligned with VideoWidget column (x: -250)
Benefit: Consistent visual layout that scales with available antenna count

No Signal Indicator
Added dedicated no_signal.png icon for connection loss state
Separate from low-signal indicators
Benefit: Clear visual distinction between weak signal and no connection

[DmtryJS]

Add some curve for non linear rssi representation.

Tested this extensively in apartment conditions with pit mode + real-time RSSI OSD debugging. Key finding: at -90 dBm the adaptive link already drops to ~1Mbps with visible freezes — essentially the edge of usability. Near the receiver I measured -35 dBm, so I set full signal to -40 dBm for accurate representation.

Examples of representation weak and average signal

[MarioFPVdev]

Just for the sake of people like me that can't see tiny icons, could you please increase the icon size or maybe add a setting for anyone who wants to do it manually?

[DmtryJS]

Just for the sake of people like me that can't see tiny icons, could you please increase the icon size or maybe add a setting for anyone who wants to do it manually?

Hi Mario! Unfortunately, I don't see how to flexibly implement an icon size setting. There are a few problems: layers have fixed coordinates, so when changing the size of one element, the others need to be moved manually as well.
But I'll try to increase these icons to 64px. Currently, they are 24px, just like the rest of the icons. The default icons were 96px, so 64px seems like a good compromise. Generally, it would be good to display a numeric RSSI value here, perhaps a combined value for all available antennas. This would be useful, alongside the bitrate.

[bd4]

64px sounds good to me. I think the old icons were too big/distracting, and I agree with Mario that the new ones seem a little small at 24px.