Add Sfm camera repair interface

[ehallein]

A reconstruction often comes out mostly right: a few cameras sit in the wrong place and a few images never register. This adds a way to fix just those, against the rest of the model, without reconstructing again. Every step works on bearings, so pinhole, fisheye and equirect cameras all go through the same path. There is a new Repair tab on the Reconstruction Editor. See camera-repair.md for instructions. I have it used to repair real reconstructions already.

What's in it

• Mapper::repair / spirula sfm repair
  • Re-places named cameras (--replace).
  • Snaps hand-placed poses (--hints).
  • Registers missing images (--add, --add-missing).
  • Optionally audits every camera (--audit).
  • Targets are matched against the model first, and the new pairs are appended to matches.bin (the original is kept as .orig).
  • The result is fitted back onto the untouched cameras, so the model's frame stays put.
• Editor Repair tab
  • Re-place selected cameras, or move them by hand (G/R) and snap them.
  • Check every camera.
  • Register missing images.
  • The result is previewed in colour, then kept (with .orig backups and a reopen) or discarded with undo intact.
• Camera photo panel: Previous/Next, Look through (puts the view at the camera with its lens), and the photo laid over the viewport.
• Missing images
  • A list of the images with features but no camera.
  • Guess places takes a pose from another model in sparse/ (aligned on the cameras they share) or interpolates between file-order neighbours.
  • Place at view sets a pose by hand.
  • Placed images are retried as their neighbours register, so a whole missing stretch goes in one run.
• Docs: docs/notes/camera-repair.md (user guide) and the repair section of src/sfm/README.md.

Testing

• sfm_repair_test: pinhole and equirect scenes; named, hinted and audited cameras return to their poses, and missing images register.
• Real 40-frame equirect: repaired cameras land within 0.01°.
• Real 30-frame pinhole: all cameras within 0.26° after their matches were stripped.
• 1,092-frame equirect boardwalk, run in the GUI on a test copy:
  • 49 missing images (46 of which had split off into their own small model) all registered, from 1,043 to 1,092 cameras.
  • Existing cameras moved at most 0.05% of the scene size and 0.12°.
  • The camera path runs evenly through both former gaps.
• Comment, i18n (all 13 languages), font coverage and citation checks pass.

Limitations

• Binary COLMAP models only.
• Uses the default matcher.
• Cameras added in the preview can't be selected.
• map --resume still doesn't read rigs.txt.