stl2step v0.7.1-wip

• The Image → STEP tab now carries ImageToSketch 0.9.1 (was 0.9.0). A typed camera distance is forgiving: a photo straight from the phone measures the distance itself (lens data first; a typed value is only compared with it); a roughly right typed distance scales the outline evenly instead of bending it (from 1 m, 10 % out costs about 1.6 % on a 140 mm tall part); with neither, a phone's main camera is assumed instead of an error. The messages say what 10 % in the distance and 1 mm in the height cost, and question a typed distance far from what the token's size suggests.
• Fixed: "Nothing to write: no outline could be built". With 140 mm height and 1000 mm typed for a photo taken from about 30 cm, the side-wall correction tangled the outline. It is now skipped (with a message) when the camera's position is too uncertain, and the STEP error, if it still happens, says why.
• Height settings next to Convert: Part's top above the token, Camera distance and Part has straight vertical sides moved from the Scale card to just above Convert to STEP (page text only; same field names). Hidden with the other token fields when the scale comes from something else. tools/height_next_to_convert.py (from the module) was run on app/webui.py; it is kept and is safe to run twice.
• Checked: this Linux machine, the full automated suite (see below); the module's own checks were done in the ImageToSketch chat on STL2STEP 0.4.2-wip, not on this version. Real photos of tall parts are not tested (simulated photos only): measure one size with calipers. Not run on Windows or macOS.