Add support tickets that work with private threads

Members open a ticket from a panel in the ticket channel: one button per
category (a dropdown past five), then a short form. Each ticket is a private
thread named after the category, number and opener, with a first message
that mentions the category's staff role so its members join, and Claim and
Close buttons.

- Claim: staff (the category's role, or Manage Threads / Manage Server)
  take a ticket; the first message shows who has it.
- Close: the opener or staff close it, with an optional reason. The thread
  is locked and archived, and the log channel gets a summary and a .txt
  transcript of the whole thread.
- /ticket add|remove|claim|close inside a ticket; /tickets setup,
  /tickets category add|remove|list and /tickets panel for admins.
- Per-member limit on open tickets (default 1), per-server ticket numbers
  handed out atomically, a deleted thread closes its ticket.
- The dashboard asks the bot to post or refresh the panel through
  ticket_commands (LISTEN/NOTIFY, like music); the listener reconnects if
  the database connection drops.
- Setup warns about missing bot permissions in the ticket and log channels.

The flows live in internal/tickets behind small Discord and store
interfaces, with unit tests on fakes; the repo and the listener have
integration tests (-tags integration, TICKETS_TEST_DB).

Needs the ticket tables (velox-dashboard-api migration 000016_tickets).
.gitignore gains the /tldr benchmark rules so private chat exports and
benchmark results on disk can't be committed from this branch.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

README.md

@@ -9,6 +9,7 @@ It currently includes:
 - Meeting rooms (voice lobby → auto-created temporary voice channels)
 - Scheduling (1:1 sessions with DM invites + reaction-based accept/decline/reschedule)
 - Projects (list/create projects + helpers)
+- Support tickets (a panel with categories, a private thread per ticket, claim/close, transcripts to a log channel)
 - Music (Lavalink-powered `/play`, `/queue`, `/volume`)
 - Twitch live notifications (per-guild `/config` setup)
 - Welcome messages, DMs, and default role assignment (per-guild `/config` setup)
@@ -98,6 +99,12 @@ just down    # stop postgres
   - `/schedule create`, `/schedule list`, `/schedule reschedule`
 - **Projects**
   - `/projects list`, `/projects create`, `/projects add-helper`
+- **Tickets**
+  - `/tickets setup channel:#tickets [log-channel] [staff-role]` — Where tickets open and closed ones are logged (**Manage Server**)
+  - `/tickets category add|remove|list` — One panel button per category, each with its own staff role (**Manage Server**)
+  - `/tickets panel` — Post or refresh the panel (**Manage Server**)
+  - `/ticket add`, `/ticket close [reason]` — Opener or staff; `/ticket claim`, `/ticket remove` — staff
+  - The bot needs View Channel, Send Messages, Embed Links, Create Private Threads, Send Messages in Threads and Manage Threads in the ticket channel, and Attach Files in the log channel. Give the staff role Manage Threads there too, so staff see every ticket.
 - **Music** (requires **DJ** role)
   - `/play`, `/queue`, `/volume`
 - **Moderation** (focused + practical)