feat(fase-11): item_tags + shopping_item_tags schema (11.1)

Migration 022 adds two new tables for collective-scoped item tags plus the
many-to-many bridge to shopping_items. Tags carry a colour from an 8-preset
palette enforced by CHECK. RLS uses is_member for SELECT (guests can see)
and is_active_member for writes (guests are read-only). A new STABLE helper
item_collective_id(uuid) resolves the parent collective in a single function
call so the shopping_item_tags policies do not chain two STABLE lookups.

Both tables join the supabase_realtime publication with REPLICA IDENTITY
FULL, matching the shape of 007 for shopping_items / shopping_lists.

pgTAP 014 covers schema invariants (publication, replica identity, unique
+ CHECK constraints, cascade behaviour for both tag delete and collective
delete). Per-role RLS semantics will be covered by the Vitest integration
suite in the next commit — pgTAP runs as postgres which bypasses RLS.

Types: ItemTag, ItemWithTags + ItemTagColor in domain.ts; item_tags,
shopping_item_tags, item_collective_id added by hand to the curated
database.ts (the supabase CLI is not installed locally; just db-types is
gated and skips with a notice).

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

supabase/migrations/022_item_tags.sql

@@ -0,0 +1,101 @@
+-- Migration 022: item_tags + shopping_item_tags (Fase 11)
+--
+-- Tags are scoped to a collective (a string in two collectives = two distinct
+-- rows). No hierarchy. Color from an 8-preset palette so the UI can render
+-- without a custom picker. The shopping_item_tags many-to-many is enforced by
+-- RLS via the parent shopping_items row (which itself uses list_collective_id).
+--
+-- Reads (select): is_member — guests included, so they see tags too.
+-- Writes (insert/update/delete): is_active_member — guests are read-only,
+-- matching the policy shape used by shopping_items / shopping_lists.
+
+-- ── item_tags ────────────────────────────────────────────────────────────────
+
+CREATE TABLE public.item_tags (
+    id            uuid        PRIMARY KEY DEFAULT gen_random_uuid(),
+    collective_id uuid        NOT NULL REFERENCES public.collectives(id) ON DELETE CASCADE,
+    name          text        NOT NULL,
+    color         text        NOT NULL DEFAULT 'slate'
+                              CHECK (color IN ('slate','red','amber','green','sky','indigo','pink','stone')),
+    created_at    timestamptz NOT NULL DEFAULT now(),
+    UNIQUE (collective_id, name)
+);
+
+ALTER TABLE public.item_tags ENABLE ROW LEVEL SECURITY;
+
+CREATE INDEX item_tags_collective_idx ON public.item_tags (collective_id);
+
+CREATE POLICY item_tags_select
+    ON public.item_tags FOR SELECT
+    USING (public.is_member(collective_id));
+
+CREATE POLICY item_tags_insert
+    ON public.item_tags FOR INSERT
+    WITH CHECK (public.is_active_member(collective_id));
+
+CREATE POLICY item_tags_update
+    ON public.item_tags FOR UPDATE
+    USING  (public.is_active_member(collective_id))
+    WITH CHECK (public.is_active_member(collective_id));
+
+CREATE POLICY item_tags_delete
+    ON public.item_tags FOR DELETE
+    USING (public.is_active_member(collective_id));
+
+-- ── shopping_item_tags ───────────────────────────────────────────────────────
+
+CREATE TABLE public.shopping_item_tags (
+    item_id uuid NOT NULL REFERENCES public.shopping_items(id) ON DELETE CASCADE,
+    tag_id  uuid NOT NULL REFERENCES public.item_tags(id) ON DELETE CASCADE,
+    PRIMARY KEY (item_id, tag_id)
+);
+
+ALTER TABLE public.shopping_item_tags ENABLE ROW LEVEL SECURITY;
+
+CREATE INDEX shopping_item_tags_tag_idx ON public.shopping_item_tags (tag_id);
+
+-- Helper: resolve the collective for a shopping_items row.
+-- STABLE + SECURITY DEFINER mirrors public.list_collective_id (Migration 005).
+-- We inline it here rather than chain two calls inside policies so the planner
+-- gets a single STABLE function call per row.
+CREATE OR REPLACE FUNCTION public.item_collective_id(p_item_id uuid)
+RETURNS uuid
+LANGUAGE sql
+STABLE
+SECURITY DEFINER
+SET search_path = public
+AS $$
+    SELECT sl.collective_id
+    FROM   public.shopping_items si
+    JOIN   public.shopping_lists sl ON sl.id = si.list_id
+    WHERE  si.id = p_item_id;
+$$;
+
+CREATE POLICY shopping_item_tags_select
+    ON public.shopping_item_tags FOR SELECT
+    USING (public.is_member(public.item_collective_id(item_id)));
+
+CREATE POLICY shopping_item_tags_insert
+    ON public.shopping_item_tags FOR INSERT
+    WITH CHECK (
+        public.is_active_member(public.item_collective_id(item_id))
+        -- Prevent attaching a tag from a different collective than the item.
+        AND public.item_collective_id(item_id) = (
+            SELECT collective_id FROM public.item_tags WHERE id = tag_id
+        )
+    );
+
+CREATE POLICY shopping_item_tags_delete
+    ON public.shopping_item_tags FOR DELETE
+    USING (public.is_active_member(public.item_collective_id(item_id)));
+
+-- ── Realtime publication ─────────────────────────────────────────────────────
+-- Mirror the shape used by migration 007: add both tables and set REPLICA
+-- IDENTITY FULL so UPDATE/DELETE events carry the full row (needed for the
+-- item-id-based client filtering used by the lists detail view).
+
+ALTER PUBLICATION supabase_realtime ADD TABLE public.item_tags;
+ALTER PUBLICATION supabase_realtime ADD TABLE public.shopping_item_tags;
+
+ALTER TABLE public.item_tags          REPLICA IDENTITY FULL;
+ALTER TABLE public.shopping_item_tags REPLICA IDENTITY FULL;