Two new optional fields on Spool: free-text `category` (max 50) and
`low_stock_threshold_pct` (1-99). Powers the "differentiate critical
spools from prototype spools and alert at different thresholds" use
case from #729 without taking on the full multi-tag taxonomy + auto-
apply rules + per-tag alert system the ticket originally proposed.
Form gains:
- Category input with datalist autocomplete sourced from categories
already in use, so casing/spelling stays consistent.
- Per-spool low-stock threshold input. Empty = global default; the
global value renders as the placeholder.
Inventory page:
- New category filter chip (hidden until at least one spool carries
a category — keeps the chip row uncluttered).
- Stat-card "Low Stock" count and the "Low Stock" filter both honour
the per-spool override.
Plus: rename "Delete Tag" button to "Clear RFID Tag" (the original
ticket reporter mistook it for a taxonomy-tag delete; the button
actually clears the RFID UID/UUID off the spool record). Toast key
renamed from `tagDeleted` to `rfidCleared`.
i18n: full translations across all 8 locales.
Tests: 9 new backend schema tests (defaults, partial-update, range
rejection, max-length); 2 new frontend tests (per-spool threshold
pulls extra spools into low-stock count, filter chip hidden when no
categories exist).
A single legacy spool with a 7-char rgba ('FFFFFFF', missing one F)
caused GET /api/v1/inventory/spools to 500 with a pydantic
ResponseValidationError, leaving the reporter with a blank Filaments
page and "Add Spool" silently failing. Root cause spans three layers:
1. Write path: SpoolUpdate.rgba had no pattern constraint (only
SpoolCreate did), so PATCH could plant malformed values in the DB.
2. Frontend: ColorSection hex input's `val.length <= 6 ? 'FF' : ''`
emitted 7-char rgba for 5-char input (XXXXX + FF = 7) and for
7-char typed input (no alpha appended).
3. Read path: SpoolResponse inherited the write-side pattern, so a
single bad row 500'd the entire list endpoint instead of being
tolerated through serialize.
SpoolUpdate.rgba now carries the same ^[0-9A-Fa-f]{8}$ pattern as
SpoolCreate. The hex input emits a fully-formed 8-char RRGGBBAA on
every keystroke — 8-char paste passes through, 7-char drops the
stray, shorter input pads RGB with '0' and appends FF alpha.
SpoolResponse.rgba is now Optional[str] with no pattern — write-side
validation is the right place for format rules; responses must
tolerate historical rows.
Tests: 16 schema tests (SpoolCreate/Update reject, SpoolResponse
tolerate), 7 frontend tests covering every input length 0–8 plus
non-hex strip. A user who already has a bad row in their DB now sees
it render with a default color instead of having to hand-edit SQLite.
maziggy