feat: forum, polymorphic comments, custom tiers, multi-invite, secrets encryption

Big feature batch driven by the super-audit findings and the user's
follow-up requests.

Schema migration 021 (folded into schema.sql Section 13):
- forum_threads + polymorphic comments table keyed on (entity_type,
  entity_id). Entity types: forum_thread, proposal, incident, policy.
  Trigger maintains forum_threads.comment_count and last_comment_at.
- space_tiers per-space with monthly_price_cents, billing_cadence,
  is_system, sort_order. Trigger seeds plus/basic/associate on every
  space INSERT and backfills existing spaces. space_members.tier_id FK
  added and backfilled from the legacy enum value.
- space_role_labels (rename/recolor built-in roles per space).
  space_custom_roles + space_member_custom_roles for non-privileged
  extra labels. RLS gates by admin/board.
- space_invites: multi-code invites with expires_at, max_uses,
  uses_count, is_enabled. Legacy spaces.invite_code backfilled as a
  permanent enabled invite.
- secrets.encrypted_value bytea + encryption_version. Secrets RLS
  tightened. New comms_channels INSERT policy: any member can create;
  default channels are protected from deletion.
- knowledge_base.render_markdown boolean (default true).

Secrets encryption-at-rest:
- AES-256-GCM in lib/secrets/crypto.ts. Master key from
  SECRETS_ENCRYPTION_KEY env (64 hex chars).
- New revealSecret(id) server action: only path to plaintext, writes
  secret.revealed to activity_log.
- /ops/page.tsx no longer selects value or encrypted_value on the list
  endpoint - the original screenshot bug where ciphertext was already
  in the page bundle before "Reveal" is fixed.

UI:
- /forum index, /forum/new, /forum/[id]. Pin/lock/delete actions for
  admin/board.
- CommentThread component embedded on /proposals/[id], /incidents/[id],
  /policies/[slug]. Markdown rendering via react-markdown + remark-gfm.
- /comms sidebar: inline "+ New channel" form.
- /ops KB: row click opens markdown-rendering viewer modal.
- /settings: new Tiers tab and Invites tab. Inline price edit and
  archive/delete on tiers; copy/enable/disable/delete on invites.
- AtlasLogo replaces the terminal icon on the landing nav and footer.
  public/logo.svg wired as the favicon in app/layout.tsx metadata.
- Sidebar has a Forum nav link.

Server actions added:
- lib/actions/forum.ts, comms.ts, tiers.ts, roles.ts, invites.ts.
- lib/actions/secrets.ts rewritten with updateSecret + revealSecret.

Auth flow:
- joinSpace honors codes from space_invites first (enabled, expiry,
  use cap), falls back to legacy spaces.invite_code, increments
  uses_count on success.

Env:
- SECRETS_ENCRYPTION_KEY documented in .env.example and set on the
  Droplet's /opt/hackerspace-ops/.env.production.

README: live site link added (https://hackerspace.sh).

266/266 unit tests pass. Production build clean. Migration 021 will be
applied on the next deploy via /opt/hackerspace-ops/deploy.sh's
idempotent migration runner.

CHANGELOG.md

@@ -5,6 +5,20 @@ All notable changes to this project are documented here. Format follows [Keep a
 ## [Unreleased]
 
 ### Added
+- **Forum** at `/forum`: top-level discussion threads with categories, pinning, locking. Author or admin/board can edit; admin can delete.
+- **Polymorphic comment threads** on proposals, incidents, and policies. New `comments` table keyed on `(entity_type, entity_id)`. Renders markdown.
+- **User-creatable chat channels**: inline "+ New channel" form in `/comms` (name, description, type). RLS now allows any member to create; default channels stay protected.
+- **Custom membership tiers with prices**: new `space_tiers` table per space. Settings -> Tiers tab to list, create, edit (including inline price edit), archive, and delete custom tiers. Built-in `plus`/`basic`/`associate` tiers seed on space creation and on existing spaces via backfill. `space_members.tier_id` FK backfilled from the legacy enum.
+- **Customizable role labels and custom org roles**: `space_role_labels` (rename/recolor built-ins per space) and `space_custom_roles` (non-privileged extra labels) with member m2m. Server actions wired; UI surface pending in a follow-up.
+- **Multi-code invites**: `space_invites` with per-code expiry, max-use cap, and enable/disable. Legacy `spaces.invite_code` backfilled as a permanent enabled invite. Settings -> Invites tab to manage. `joinSpace` honors any valid invite and increments `uses_count`.
+- **Knowledge base markdown rendering**: clicking a KB entry opens a modal that renders `content` as markdown via react-markdown + remark-gfm.
+- **AtlasLogo as the brand mark**: replaces the terminal icon on the landing nav and footer; `public/logo.svg` is the favicon.
+- Live site link in `README.md`: <https://hackerspace.sh>.
+
+### Changed
+- **Secrets vault is now encrypted at rest**: AES-256-GCM with a per-secret IV using a `SECRETS_ENCRYPTION_KEY` env var. The /ops list endpoint no longer sends plaintext or ciphertext to the client. A new `revealSecret(id)` server action is the only path to plaintext and writes a `secret.revealed` row to `activity_log`. Existing legacy plaintext rows continue to work.
+
+### Added (continued)
 - Production deployment to a self-hosted DigitalOcean Droplet with automatic HTTPS via Caddy and Let's Encrypt.
 - GitHub Actions workflow that pushes a deploy on every commit to `main`. Migrations are applied automatically via `_migrations_applied` tracking.
 - Daily encrypted `pg_dumpall` backup cron, retained 14 days, written to the persistent block volume.