feat(fase-9): migration 015 — users.theme column for dark mode

Adds `theme text not null default 'system' check (theme in
('light','dark','system'))` to public.users. New users get 'system' so
the UI follows the OS preference until they opt in; existing rows
backfill via the default.

Includes pgTAP test 009 (8 assertions covering column existence/type,
default value, valid transitions, and the check constraint rejecting
unknown values). Wires the theme field into the hand-curated
database.ts type so PostgREST queries stay typed.

Also hardens `just db-types` to bail out (instead of truncating
database.ts) when the supabase CLI is missing — the recipe was silently
wiping the file on this dev machine.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Justfile

@@ -47,9 +47,20 @@ db-migrate:
 db-seed:
     docker exec -i colectivo-dev-db-1 psql -U postgres < supabase/seed.sql
 
-# Regenerate TypeScript types from Supabase schema
+# Regenerate TypeScript types from Supabase schema.
+# Writes to a tempfile first so a missing/failing `supabase` CLI does not
+# truncate the existing hand-curated database.ts (which would silently
+# break every TS consumer in the monorepo).
 db-types:
-    supabase gen types typescript --local > packages/types/src/database.ts
+    #!/usr/bin/env bash
+    set -euo pipefail
+    if ! command -v supabase >/dev/null 2>&1; then
+        echo "supabase CLI not installed — database.ts is hand-curated, edit it manually" >&2
+        exit 1
+    fi
+    tmp=$(mktemp)
+    supabase gen types typescript --local > "$tmp"
+    mv "$tmp" packages/types/src/database.ts
     echo "Types written to packages/types/src/database.ts"
 
 # Open Supabase Studio