Plain wording across panels and fix retention-bound views

[MrAlders0n]

• Drop server jargon ("retained reports", "reported receptions", "recorded packets") for plain wording: observations, Heard by N observers, Packets heard. Long caveats cut to one line in info tips.
• Consistent names: Map path vs Map all paths, Recent observations / Heard on routes, Neighbor, Multi-byte, Copy link, sentence-case analytics tabs. Route panel button is Inspect packet.
• User-facing IATA becomes area; Region label uppercased via CSS; Mesh KPI cards say Last 24h.
• Compare with hides packet overlap at 30d (raw packets don't live that long); Compare tab warns when the start is older than 7 days and uses minute precision.
• Talkers rows open the node; node panel's list is Recent packets.

Part of #94.