feat(web): edit a provider's model catalog from the console

The backend has carried a per-provider model catalog for a while — entries
with capability tags, a context window and a max output budget — and the
models API already returns both what is saved (catalog) and the vendor's
presets typed with their real capabilities (seed). Nothing rendered them, so
the only way to use the feature was hand-editing config.json.

Add an editor to both provider modals, collapsed under an "Advanced" heading
since it is opt-in: a catalog REPLACES a vendor's preset model list, so the
section stays shut until the user has a reason to open it.

- rows for each entry: name, capability chips, context window, max output
- "restore presets" seeds the draft from the vendor's preset models, so
  editing an override starts from the real values instead of a blank row
- embedding / image / asr / tts entries have no text budget, so their window
  and output inputs are hidden — and cleared if the tags change — rather than
  inviting numbers that mean nothing
- the row list scrolls on its own and each modal is height-capped, so a long
  catalog cannot push the save button off screen
- saved as a separate request, and only when the draft differs from what is
  stored: writing it on every credentials save would silently wipe a list the
  user never opened

Tests: 21 covering the seed/catalog fields the editor reads, the save
handler it posts to, and the normalization rules it relies on.