feat: add public club pages

Add publication settings for clubs and sessions, read-only public club/session pages, dashboard controls, privacy-focused public queries, docs, and tests.

Bump version to 3.3.0

src/GmRelay.Bot/Migrations/V026__add_public_club_pages.sql

@@ -0,0 +1,17 @@
+-- Public club pages and read-only schedule publication controls.
+
+ALTER TABLE game_groups
+    ADD COLUMN public_slug VARCHAR(120),
+    ADD COLUMN public_schedule_enabled BOOLEAN NOT NULL DEFAULT false,
+    ADD COLUMN public_schedule_updated_at TIMESTAMPTZ;
+
+ALTER TABLE sessions
+    ADD COLUMN is_public BOOLEAN NOT NULL DEFAULT false;
+
+CREATE UNIQUE INDEX ux_game_groups_public_slug
+    ON game_groups (lower(public_slug))
+    WHERE public_slug IS NOT NULL;
+
+CREATE INDEX ix_sessions_public_schedule
+    ON sessions (group_id, scheduled_at)
+    WHERE is_public = true AND status <> 'Cancelled';