feat(web): add private club showcases with membership flow (v3.7.0)

Implements Issue #110: game masters can now publish sessions
exclusively to a club's private showcase, gated behind a
member application and approval flow. Adds a 4-state
publication_mode (None/Catalog/ClubOnly/Both) replacing the
binary is_public, plus a club_memberships table with
Pending/Active/Rejected/Left lifecycle and partial unique
index ensuring a single Active row per (group, player).

Highlights
- V030 migration: club_memberships, publication_mode, drop
  is_public, recreate partial indexes, portfolio_games gains
  publication_mode.
- PublicationMode enum + extensions in GmRelay.Shared.
- ISessionStore gains 12 membership/showcase methods;
  AuthorizedMembershipService owns the membership flow with
  GM-only approve/reject authorization.
- PublicClub / PublicMasterProfile / PublicSession: member-
  aware queries (ClubOnly visible only to Active members).
- New pages: MyClubMemberships (/profile/memberships) and
  ClubApplications (/group/{id}/applications).
- GroupDetails and EditSession switch from a bool toggle to
  a 4-state publication_mode selector.
- NavMenu adds Moji kluby, PublicLayout adds Kluby.

Tests: 4 new test files (PublicationMode, ClubMemberships,
AuthorizedMembershipService, ClubShowcaseSource) + updates
to PublicClubPages, AuthorizedSessionService/Portfolio
service FakeSessionStore, CampaignTemplatesNavigation.
493 tests pass.

Bump version 3.6.0 -> 3.7.0 across Directory.Build.props,
compose.yaml, deploy.yml, NavMenu.razor.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/GmRelay.Bot/Migrations/V030__add_club_memberships_and_publication_mode.sql

@@ -0,0 +1,66 @@
+-- V030: Private club showcases. Adds club_memberships (member access control)
+-- and replaces sessions.is_public with a 4-state publication_mode enum.
+-- Backfills existing data: is_public=true → 'Both', is_public=false → 'None'.
+-- portfolio_games gains the same enum (default 'Both' for pre-V030 rows).
+
+-- 1. club_memberships
+CREATE TABLE club_memberships (
+    id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    group_id        UUID NOT NULL REFERENCES game_groups(id) ON DELETE CASCADE,
+    player_id       UUID NOT NULL REFERENCES players(id) ON DELETE CASCADE,
+    status          VARCHAR(20) NOT NULL DEFAULT 'Pending'
+                    CHECK (status IN ('Pending', 'Active', 'Rejected', 'Left')),
+    role            VARCHAR(20) NOT NULL DEFAULT 'Member'
+                    CHECK (role IN ('Member')),
+    message         TEXT,
+    applied_at      TIMESTAMPTZ NOT NULL DEFAULT now(),
+    decided_at      TIMESTAMPTZ,
+    decided_by      UUID REFERENCES players(id) ON DELETE SET NULL
+);
+
+-- Only one Active row per (group, player).
+-- Re-application after Rejected/Left creates a new row.
+CREATE UNIQUE INDEX ux_club_memberships_one_active
+    ON club_memberships (group_id, player_id)
+    WHERE status = 'Active';
+
+CREATE INDEX ix_club_memberships_group_status
+    ON club_memberships (group_id, status);
+
+CREATE INDEX ix_club_memberships_player_status
+    ON club_memberships (player_id, status);
+
+-- 2. sessions.publication_mode (replaces is_public)
+ALTER TABLE sessions
+    ADD COLUMN publication_mode VARCHAR(20) NOT NULL DEFAULT 'None';
+
+-- Backfill before constraint so existing data maps cleanly.
+UPDATE sessions SET publication_mode = 'Both' WHERE is_public = true;
+UPDATE sessions SET publication_mode = 'None' WHERE is_public = false;
+
+ALTER TABLE sessions
+    ADD CONSTRAINT ck_sessions_publication_mode
+    CHECK (publication_mode IN ('None', 'Catalog', 'ClubOnly', 'Both'));
+
+ALTER TABLE sessions DROP COLUMN is_public;
+
+DROP INDEX IF EXISTS ix_sessions_public_schedule;
+DROP INDEX IF EXISTS ix_sessions_showcase;
+
+CREATE INDEX ix_sessions_public_schedule
+    ON sessions (group_id, scheduled_at)
+    WHERE publication_mode IN ('Catalog', 'Both') AND status <> 'Cancelled';
+
+CREATE INDEX ix_sessions_showcase
+    ON sessions (scheduled_at, system, is_one_shot, format)
+    WHERE publication_mode IN ('Catalog', 'Both') AND status <> 'Cancelled';
+
+-- 3. portfolio_games.publication_mode
+-- Existing rows in portfolio_games keep 'Both' to stay visible to anonymous visitors.
+ALTER TABLE portfolio_games
+    ADD COLUMN publication_mode VARCHAR(20) NOT NULL DEFAULT 'Both'
+    CHECK (publication_mode IN ('None', 'Catalog', 'ClubOnly', 'Both'));
+
+CREATE INDEX ix_portfolio_games_showcase
+    ON portfolio_games (created_at DESC)
+    WHERE publication_mode IN ('Catalog', 'Both');