The seed-packet capture backend has been live since #94 (POST /seed-lots/scan
and /seed-lots/from-packet, with /capabilities reporting `vision`), but there was
no UI, so the feature Steve asked for — "take a picture of a packet and it
auto-creates" — was unreachable. This adds the mobile-first UI.

- Entry point in the Plants catalog ("Scan a packet"), shown only where
  `capabilities.vision` is on — so it's never a dead button on an instance with
  no vision model. Adds `vision` to the capabilities schema (both flags now
  default false, so a partial response hides a feature rather than failing parse).
- ScanPacketModal: two phases in one dialog. Capture uses a file input with
  `accept="image/*" capture="environment"` so a phone opens the camera directly
  (also picks an existing photo; HEIC is handled server-side). Review shows the
  extracted fields read-only for context, then an editable confirm — pick a ranked
  existing candidate (with its match reason) or create a new variety prefilled from
  the packet. Nothing commits blind, which is the whole point of the backend's
  never-auto-create design.
- New data layer (lib/seedPacket.ts): zod schemas mirroring the backend
  (SeedPacket / PacketProposal / PacketResult), the scan + confirm mutations, and
  the pure prefill helpers (newPlantDefaults / lotDefaults) — unit-tested, since
  the prefill mapping (unknown category, missing spacing, seed-count→unit) is
  where the bugs hide.
- api.ts learns to send FormData as multipart (no JSON content-type) for the
  scan upload, via a new api.postForm.

Frontend only; no backend or route change. Last open child of epic #96.

Live camera→vision→proposal verification needs a vision-configured instance
(the flow is model-gated and unreachable locally, same as the assistant);
the confirm half and all prefill logic are covered by tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01H3zbym8Doka2d7D48maSgZ

@@ -0,0 +23,4 @@
+import { LOT_UNITS, type LotUnit } from '@/lib/seedLots'
+import { cmFromSpacing, spacingFromCm, spacingUnitLabel, type UnitPref } from '@/lib/units'
+
+const categoryOptions = PLANT_CATEGORIES.map((c) => ({ value: c, label: CATEGORY_LABELS[c] }))

@@ -0,0 +44,4 @@
+  const create = useCreateFromPacket()
+  const fileInput = useRef<HTMLInputElement>(null)
+
+  const [proposal, setProposal] = useState<PacketProposal | null>(null)

@@ -0,0 +85,4 @@
+        setCategory(plant.category)
+        setSpacing(String(spacingFromCm(plant.spacingCm, unit)))
+        setDays(plant.daysToMaturity != null ? String(plant.daysToMaturity) : '')
+        setVendor(lot.vendor)

@@ -0,0 +102,4 @@
+    if (!proposal) return
+    setError(null)
+
+    // Lot validation mirrors SeedLotModal so the two paths accept the same things.

@@ -0,0 +127,4 @@
+      costCents = Math.round(c * 100)
+    }
+
+    const lot = {

@@ -0,0 +140,4 @@
+      germinationPct: null,
+      notes: '',
+    }
+

@@ -0,0 +148,4 @@
+        setError('Name the new variety, or pick an existing plant above.')
+        return
+      }
+      const spacingCm = cmFromSpacing(parseFloat(spacing), unit)

@@ -0,0 +188,4 @@
+  }
+
+  return (
+    <Modal title="Scan a seed packet" onClose={onClose} busy={busy}>

@@ -0,0 +360,4 @@
+          {error && <Alert>{error}</Alert>}
+
+          <div className="mt-1 flex justify-between gap-2">
+            <Button type="button" variant="ghost" onClick={() => setProposal(null)} disabled={busy}>

@@ -0,0 +93,4 @@
+
+// A packet has no icon or color, so a new variety created from one gets these
+// placeholders; the user can set a real icon/color later from the plant card.
+export const PACKET_PLANT_COLOR = '#4a7c3f'