[vynulldev]

What & why

Imported rekordbox Hot Cue Banks were only visible on a deck. This shows them in the web UI and the API, as decks browse them. Builds on #86 (Hot Cue Bank support).

• API: GET /api/hotcuebanks lists the live folders and banks (parent_id links the tree, seq orders siblings) with each bank's track count. GET /api/hotcuebanks/{id}/tracks lists a bank's tracks in membership order, as a deck does: duplicates kept, content not in the library left out. Each entry has its position, cue in milliseconds, loop end (only for loops), hot-cue palette colour (color_id, 0 when unset) and comment. A folder or unknown ID returns 404. Both endpoints are in the OpenAPI spec under a new Hot Cue Banks tag.
• Web UI: the library sidebar gets a HOT CUE BANKS section with the folder tree, shown only when banks exist. Selecting a bank shows its tracks with a colour column like rekordbox's (the cue's palette colour, or the default green for a cue and orange for a loop, plus a loop marker), the pad each position maps to (positions 1-8 are pads A-H, as in rekordbox and on the deck), the cue and loop end, and the comment. The text filter narrows the list by title or artist, and a row opens the track drawer. Tracks whose file is missing on this machine are listed dimmed and marked MISSING FILE, since decks aren't sent them, and a bank's track count leaves them out. Nothing is editable; the filter bar and column picker are hidden for this view.

A test covers both endpoints (tree, track count, ordering, duplicates, unresolved content, loop end, 404s). The UI was checked in headless Chromium against the link-spec Hot Cue Bank fixture: tree order, the Alpha Bank's ten tracks with pads A-H on positions 1-8, filtering, the empty bank, and switching back to the collection, with no page errors.

Hardware testing

• Tested on: Not needed: this only adds read-only API endpoints and a web UI view; nothing sent to decks changes.

Checklist

• go build ./..., go vet ./..., and go test ./... pass
• gofmt -l . is clean
• New source files carry an SPDX header (GPL-3.0-or-later)
• Tested on real hardware (deck + firmware noted above), or this change doesn't affect deck behaviour
• I agree my contribution is licensed under the project's GPLv3