docs: add full wiki with 74 pages, assets, and CI workflow

Adds the complete TREK documentation wiki covering installation,
trip planning, admin panel, MCP/AI integration, addons, and operations.

Also fixes encrypt-at-rest gaps: mapbox_access_token, Synology
credentials, per-user webhook/ntfy tokens, and photo passphrases
are now rotated by migrate-encryption.ts and stored encrypted via
settingsService.

.github/workflows/docker.yml

@@ -6,6 +6,8 @@ on:
     paths-ignore:
       - 'docs/**'
       - '**/*.md'
+      - 'wiki/**'
+      - '.github/workflows/wiki.yml'
   workflow_dispatch:
     inputs:
       bump: