Vessel lat/lon readout with copy-to-clipboard

[rolker]

Part of #143.

Operator-usability additions to CAMP centered on reading and copying vessel/coordinate
positions, requested in the #143 usability wishlist (items 1 & 2) plus follow-on
operator requests. Grouped because they share one concern — getting coordinates out of
CAMP quickly — and a single decimal-degrees copy format.

1. Live vessel lat/lon readout

Show the vessel's current latitude and longitude on the GUI, updated regularly. The
motivation is screenshot metadata: periodic screen captures taken during operations
should contain the vessel position on-frame (a timestamp is typically already visible on
the desktop, but position is not).

2. Copy-to-clipboard, across three surfaces

A consistent "copy coordinates to clipboard in decimal degrees" action, available where
operators need it:

• Vessel readout — a "Copy" button next to the lat/lon readout (item 1) copies the
  current vessel position.
• Map context menu — right-clicking the map adds a "Copy coordinates" entry that copies
  the lat/lon of the clicked point.
• Waypoint details view — a "Copy" button placed above the existing "Update" button
  copies that waypoint's coordinates.

Notes / scope

• Source the vessel position from the same vessel-pose stream CAMP already renders the boat
  from (verify the topic/frame in src/camp/ before implementing — don't assume).
• The clicked-point and waypoint coordinates come from the existing map projection / mission
  model — reuse those, don't recompute.
• Decimal degrees for all copy actions, for consistency; on-screen readout format TBD
  (DD vs DM — worth a quick decision during implementation).
• Pure UI addition; no new ROS interfaces expected.

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Authored-By: Claude Code Agent
Model: Claude Opus 4.8 (1M context)