tools: train identity LoRAs from a character profile in the studio

IP-Adapter conditioning drifts on long shots and profile angles, so the studio now
has the middle step: train a LoRA straight from the profile's reference crops and
apply it to the generation.

`POST /v1/loras/train` already resolves images server-side from `character: <name>`,
so the trainer sees exactly the crops you reviewed and pruned — no re-upload. The
job runs detached (`wait: false`); the studio polls `/v1/loras/progress`, persists
the server job id per LoRA and re-attaches to a run still in flight after a client
restart instead of starting a second one, resubmitting to resume from checkpoint
when a job was interrupted.

CLI: `train`, plus `--lora NAME[:WEIGHT]` / `--image-lora` on `video` and a
`--train` flag on `demo` for extract -> train -> generate in one command.
Web UI: a training panel (target, steps, rank, resolution, frames, LR, QLoRA
toggle, cancel) and a LoRA multi-select on the scene panel.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0182DhR1eFNPQyGmDrpHbedY