feat(uat-batch-3): wave-1 primitives — DatePicker, DateTimePicker, FileInputButton, ColumnPicker hideAll

Builds the foundational primitives that subsequent waves depend on.
None of these introduce new deps — date-fns, react-day-picker, and
shadcn Calendar were already in the tree.

- `<DatePicker>` and `<DateTimePicker>` in src/components/ui — desktop
  popover wrapping the existing shadcn Calendar (caption-dropdown nav
  so reps can jump months/years for the SkipAheadBanner backfill UX),
  mobile native input via useIsMobile. Drop-in for `<Input type=date>`
  / `<Input type=datetime-local>`.
- `<FileInputButton>` in src/components/ui — styled Button + hidden
  input, replaces browser-default file picker UI. Most queued sweep
  sites already used the hidden-input + Button-trigger pattern; the
  primitive lands for any new caller plus consistent filename display
  + clear button.
- ColumnPicker `hideAll()` footer item — symmetric to existing
  `showAll()`, with the same visibility gate. Lands platform-wide via
  the shared component.
- Migrated highest-leverage call sites to the new primitives:
  * MilestoneAdvanceButton (backfill UX)
  * Reminder form (datetime-local → DateTimePicker)
  * Snooze dialog (datetime-local → DateTimePicker)
  * External-EOI upload dialog (date + file picker)
  * Payments section (received-on date)
- Remaining 15+ date-input call sites parked for a follow-up sweep —
  several use react-hook-form `register` patterns that need careful
  migration to the new controlled-value contract.

tsc clean. 1419/1419 vitest pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/interests/interest-tabs.tsx

@@ -11,7 +11,7 @@ import { parsePhone } from '@/lib/i18n/phone';
 
 import type { DetailTab } from '@/components/shared/detail-layout';
 import { Button } from '@/components/ui/button';
-import { Input } from '@/components/ui/input';
+import { DatePicker } from '@/components/ui/date-picker';
 import { Popover, PopoverContent, PopoverTrigger } from '@/components/ui/popover';
 import { NotesList } from '@/components/shared/notes-list';
 import { InlineEditableField } from '@/components/shared/inline-editable-field';
@@ -315,13 +315,12 @@ function MilestoneAdvanceButton({
           <label className="text-xs font-medium" htmlFor="milestone-date">
             Date completed
           </label>
-          <Input
+          <DatePicker
             id="milestone-date"
-            type="date"
             value={date}
-            max={new Date().toISOString().slice(0, 10)}
-            onChange={(e) => setDate(e.target.value)}
-            className="h-9"
+            toDate={new Date()}
+            onChange={setDate}
+            placeholder="Pick a date"
           />
           <p className="text-[11px] text-muted-foreground">
             Defaults to today — back-date if the event happened earlier.