feat(client-archive): smart-archive backend foundation (dossier + archive + restore)

The first slice of the smart-archive project. Replaces the dumb DELETE
client flow with a deliberate "look before you leap" pattern:

- New columns on clients: archived_by, archive_reason, archive_metadata
  (jsonb capturing every decision made during archive, so restore can
  attempt reversal). Migration 0043.
- client-archive-dossier.service builds a structured snapshot of "what's
  at stake" for a given client: pipeline interests, berths under offer
  (with next-in-line interests for the notification), yachts owned,
  active reservations, outstanding invoices, signed/in-flight Documenso
  envelopes, portal user, company memberships. Classifies the client as
  low-stakes or high-stakes based on pipeline stage (HIGH_STAKES_STAGES
  = deposit_10pct + later) so the bulk wizard knows which clients to
  prompt individually.
- client-archive.service.archiveClientWithDecisions takes the operator's
  decisions and applies them in a single transaction. Persists the
  decision log into archive_metadata for restore. Auto-handles portal
  user revocation + company membership end-dating; everything else is
  caller-driven. Surfaces external cleanups (Documenso void) for the
  caller to queue.
- client-restore.service.getRestoreDossier classifies each persisted
  decision as autoReversible / reversibleWithPrompt / locked based on
  the current state of the world (berth still available? new owner has
  active interests on the yacht? etc). restoreClientWithSelections
  applies reversals + un-archives the client.
- 4 API routes wire the services to HTTP. The existing /restore
  endpoint is upgraded to use the smart restore but stays
  backwards-compatible: clients archived before this feature have no
  archive_metadata so the dossier returns empty, and a POST with no
  body just un-archives them — same as before.

UI work + bulk variant + hard-delete + Documenso cleanup queueing land
in follow-on commits.

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

src/lib/db/migrations/0043_client_archive_metadata.sql

@@ -0,0 +1,30 @@
+-- Smart-archive feature — add columns that capture WHO archived a client,
+-- WHY, and WHAT decisions they made along the way (for the restore
+-- wizard to attempt reversal).
+--
+-- archived_at already exists (since the original schema). The three new
+-- columns are all nullable and default-friendly so existing archived
+-- rows backfill cleanly: their reason/metadata stays NULL, which the
+-- service treats as "legacy archive (no smart-archive metadata)".
+
+ALTER TABLE clients ADD COLUMN IF NOT EXISTS archived_by text;
+ALTER TABLE clients ADD COLUMN IF NOT EXISTS archive_reason text;
+ALTER TABLE clients ADD COLUMN IF NOT EXISTS archive_metadata jsonb;
+
+-- archived_by FK is SET NULL on user delete so the audit trail outlives
+-- staff turnover. Not VALID immediately to keep the lock window short;
+-- VALIDATE after the column is in place.
+DO $$
+BEGIN
+  IF NOT EXISTS (
+    SELECT 1 FROM pg_constraint WHERE conname = 'clients_archived_by_fk'
+  ) THEN
+    ALTER TABLE clients
+      ADD CONSTRAINT clients_archived_by_fk
+      FOREIGN KEY (archived_by) REFERENCES "user"(id)
+      ON DELETE SET NULL
+      NOT VALID;
+  END IF;
+END$$;
+
+ALTER TABLE clients VALIDATE CONSTRAINT clients_archived_by_fk;