[christmas] Add backfill UI and server function for recording past draws

[gazure]

Adds a Backfill a past year section to the Manage page, letting administrators enter who gave to whom in years that predate the app.

Once recorded, a backfilled year is indistinguishable from a normally drawn one: the "no repeat receivers" constraint can see it, and its letter is excluded from future draws. Entries are stored through the same revision counter as a regular draw, so recording the same year twice produces a second revision rather than overwriting the first.

The form lays out one row per pool member in a responsive grid. Receivers are chosen from a dropdown; leaving a row blank omits that person from the record, since old paper records are often incomplete. Duplicate receivers are flagged inline before saving rather than surfaced as a server error. The year and letter fields are editable, and if a record already exists for the chosen pool and year a notice appears with a link to load it for editing.

On the server side, record_past_draw validates that the submitted pairings form a valid partial permutation — no self-gifts, no giver appearing twice, no receiver appearing twice — before inserting. config and seed are left null rather than invented, which causes the pool page to omit the "How it was drawn" line for those years instead of displaying something untrue.

[gazure]

• [christmas] Add backfill UI and server function for recording past draws #389 👈 (View in Graphite)
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[gazure]

Merge activity

• Jul 25, 4:19 PM UTC: @gazure merged this pull request with Graphite.