feat(booking-templates): per-company opt-in hiding of system templates (#2004)

* feat(booking-templates): per-company opt-in hiding of system templates

Users cannot delete or hide the 26 standard konteringspaket, which clutter
the settings panel and every template picker. Deletion stays off the table
(shared global rows); instead a company can now hide individual system
templates for itself only.

- New booking_template_hidden table (insert=hide, delete=unhide), RLS gated
  on active company + write role; nothing hidden by default
- POST/DELETE /api/settings/booking-templates/[id]/hide (system templates
  only; company/team templates keep their real delete path)
- List route decorates rows with per-company is_hidden; pickers filter them
  out; the settings panel shows hidden ones in a collapsed restore section
  so hiding is never silent
- Classified in full-archive-export exclusions (UI preference, not
  rakenskapsinformation)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PU1KN431c9gp5zKvFaa1NL

* fix(booking-templates): idempotent re-hide, system-only RLS insert, hidden filter in bulk-book

Skeptic + CodeRabbit findings on #2004, one pass:

- hide upsert now passes ignoreDuplicates (DO NOTHING): the table has no
  UPDATE policy on purpose, so the DO UPDATE conflict arm turned a
  concurrent re-hide into an RLS 42501/500; pg test pins the conflict shape
- bth_insert policy additionally requires the referenced template to be an
  active system template (migration is unmerged, edited in place); negative
  pg test for company templates
- BulkBookDialog excludes templates hidden by the company (was reading the
  table directly and ignoring hides)
- panel shows the failure toast when the hide/unhide fetch itself rejects
- picker category chips built from the hidden-filtered list

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PU1KN431c9gp5zKvFaa1NL

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

lib/reference-data/fetchers.ts

@@ -42,8 +42,15 @@ export class ReferenceFetchError extends Error {
   }
 }
 
-/** A booking_templates row as the list route returns it, with its last-used stamp. */
-export type BookingTemplateWithUsage = BookingTemplateLibrary & { last_used_at: string | null }
+/**
+ * A booking_templates row as the list route returns it, with its last-used
+ * stamp and the per-company hidden flag. `is_hidden` templates stay in the
+ * payload so the settings panel can offer restore; pickers filter them out.
+ */
+export type BookingTemplateWithUsage = BookingTemplateLibrary & {
+  last_used_at: string | null
+  is_hidden: boolean
+}
 
 export async function fetchFiscalPeriods(companyId: string): Promise<FiscalPeriod[]> {
   const supabase = createClient()