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.

app/(app)/forum/new/new-thread-form.tsx

@@ -0,0 +1,83 @@
+'use client'
+
+import { useState } from 'react'
+import { useRouter } from 'next/navigation'
+import { toast } from 'sonner'
+import { createForumThread } from '@/lib/actions'
+
+const CATEGORIES = [
+  { value: 'general', label: 'General' },
+  { value: 'announcements', label: 'Announcements' },
+  { value: 'projects', label: 'Projects' },
+  { value: 'help', label: 'Help' },
+  { value: 'feedback', label: 'Feedback' },
+  { value: 'off-topic', label: 'Off topic' },
+]
+
+export function NewThreadForm() {
+  const router = useRouter()
+  const [title, setTitle] = useState('')
+  const [body, setBody] = useState('')
+  const [category, setCategory] = useState('general')
+  const [saving, setSaving] = useState(false)
+
+  async function handleSubmit(e: React.FormEvent) {
+    e.preventDefault()
+    if (!title.trim()) return
+    setSaving(true)
+    const result = await createForumThread({ title: title.trim(), body: body.trim() || undefined, category })
+    setSaving(false)
+    if ('error' in result && result.error) { toast.error(result.error); return }
+    if ('id' in result && result.id) {
+      toast.success('Thread created')
+      router.push(`/forum/${result.id}`)
+    }
+  }
+
+  return (
+    <form onSubmit={handleSubmit} className="bg-card border border-border rounded p-5 space-y-4">
+      <div>
+        <label className="font-mono text-[10px] tracking-widest text-muted-foreground uppercase block mb-1">Title</label>
+        <input
+          type="text"
+          value={title}
+          onChange={e => setTitle(e.target.value)}
+          maxLength={200}
+          required
+          autoFocus
+          className="w-full bg-background border border-border text-foreground font-sans text-sm rounded px-3 py-2 focus:outline-none focus:border-primary"
+        />
+      </div>
+      <div>
+        <label className="font-mono text-[10px] tracking-widest text-muted-foreground uppercase block mb-1">Category</label>
+        <select
+          value={category}
+          onChange={e => setCategory(e.target.value)}
+          className="w-full bg-background border border-border text-foreground font-sans text-sm rounded px-3 py-2 focus:outline-none focus:border-primary"
+        >
+          {CATEGORIES.map(c => <option key={c.value} value={c.value}>{c.label}</option>)}
+        </select>
+      </div>
+      <div>
+        <label className="font-mono text-[10px] tracking-widest text-muted-foreground uppercase block mb-1">Body (markdown)</label>
+        <textarea
+          value={body}
+          onChange={e => setBody(e.target.value)}
+          rows={8}
+          maxLength={20000}
+          placeholder="Markdown supported. Headings, lists, code blocks, links."
+          className="w-full bg-background border border-border text-foreground font-sans text-sm rounded px-3 py-2 focus:outline-none focus:border-primary"
+        />
+      </div>
+      <div className="flex items-center gap-2 justify-end">
+        <button
+          type="submit"
+          disabled={saving || !title.trim()}
+          className="bg-primary text-white text-xs font-sans px-3 py-1.5 rounded hover:bg-primary/90 transition disabled:opacity-50"
+        >
+          {saving ? 'Posting...' : 'Post thread'}
+        </button>
+      </div>
+    </form>
+  )
+}

app/(app)/forum/new/page.tsx

@@ -0,0 +1,16 @@
+import Link from 'next/link'
+import { NewThreadForm } from './new-thread-form'
+
+export default function NewThreadPage() {
+  return (
+    <div className="p-4 md:p-6 max-w-3xl">
+      <div className="mb-6">
+        <Link href="/forum" className="font-mono text-[11px] tracking-widest text-muted-foreground hover:text-foreground uppercase">
+          ← Forum
+        </Link>
+        <h1 className="font-mono text-sm tracking-widest uppercase text-muted-foreground mt-2">New thread</h1>
+      </div>
+      <NewThreadForm />
+    </div>
+  )
+}