Add pages API: model, controller, routes, preview (steps 4/6/7/8)

Backend for the CMS page builder, all under the existing /api/v1:

- pages.model: authoritative save gate — validates blocks against the
  registry and sanitizes them on every create/update; maps rows to/from the
  grouped API shape (metadata / settings); slug validated + reserved-checked
  at create and immutable after; `protected` can be set true via PATCH but
  only cleared via the unprotect path; published_at stamped on first publish.
- sanitizeBlocks: post-validation normalizer (applies each block's sanitize,
  stamps version, defaults visible, recurses container slots).
- reservedSlugs: guards page slugs from shadowing named routes/API namespaces.
- Admin routes (staff-gated): GET/POST /pages, GET/PATCH/DELETE /pages/:id,
  POST /pages/:id/unprotect (password step-up, verified against the caller's
  own hash, never logged), POST /pages/:id/preview (1h token). Audit-logs
  create/publish/unpublish/protect/unprotect/delete.
- Public routes: GET /public/pages/:slug (published; staff see drafts; site-
  mode gated) and GET /public/pages/:id/preview/:token (ungated, token is the
  access control). Preview token primitives added to auth/token.js.
- Swagger annotations for all new endpoints.

Verified end-to-end: model integration test against the dev DB (sanitize,
invalid-block rejection, slug immutability, protected/unprotect, dup/reserved
slug, published_at) + authenticated HTTP smoke (201 create, 400 invalid
blocks, publish, public slug fetch, preview mint+fetch, 403 delete-protected,
401 wrong-password unprotect).

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

server/src/blocks/index.js

@@ -10,6 +10,7 @@
 
 const registry = require('./registry')
 const { validateBlocks, MAX_BLOCKS, MAX_SUBBLOCKS } = require('./validateBlocks')
+const { sanitizeBlocks } = require('./sanitizeBlocks')
 
 // ── Wave 1 block definitions (self-register on require) ────────────────
 require('./types/heading')
@@ -23,6 +24,7 @@ require('./types/quote')
 module.exports = {
   ...registry,
   validateBlocks,
+  sanitizeBlocks,
   MAX_BLOCKS,
   MAX_SUBBLOCKS,
 }

server/src/blocks/sanitizeBlocks.js

@@ -0,0 +1,47 @@
+// Normalize + sanitize a validated blocks array before persisting. Runs AFTER
+// validateBlocks (which guarantees the envelope/prop shape), so this can assume
+// well-formed input and focus on: applying each block's registry `sanitize`
+// normalizer (e.g. rich_text runs its html through the allowlist), stamping the
+// registry `version`, defaulting `visible` to true, and recursing one level into
+// container slots. Returns a new array; never mutates the input.
+
+const { getBlock } = require('./registry')
+
+function sanitizeBlocks(blocks) {
+  if (!Array.isArray(blocks)) return []
+  return blocks.map(sanitizeOne)
+}
+
+function sanitizeOne(block) {
+  const def = getBlock(block.type)
+  if (!def) return block // unreachable after validation, but stay defensive
+
+  let props = block.props && typeof block.props === 'object' ? { ...block.props } : {}
+
+  // Recurse into container slots first (leaf sub-blocks get sanitized too).
+  if (def.container) {
+    for (const slot of def.containerSlots) {
+      if (Array.isArray(props[slot])) props[slot] = props[slot].map(sanitizeOne)
+    }
+  }
+
+  // Apply the block's own normalizer last (operates on its scalar props).
+  if (def.sanitize) {
+    try {
+      props = def.sanitize(props)
+    } catch {
+      // Leave props as-is; validation already passed, a sanitize throw shouldn't
+      // block the save.
+    }
+  }
+
+  return {
+    id: block.id,
+    type: block.type,
+    version: Number.isInteger(block.version) ? block.version : def.version,
+    visible: block.visible !== false,
+    props,
+  }
+}
+
+module.exports = { sanitizeBlocks }