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/wiki.yml

@@ -0,0 +1,26 @@
+name: Deploy Wiki
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'wiki/**'
+      - '.github/workflows/wiki.yml'
+  workflow_dispatch:
+
+permissions:
+  contents: write
+
+concurrency:
+  group: wiki-deploy
+  cancel-in-progress: true
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Publish to GitHub wiki
+        uses: Andrew-Chen-Wang/github-wiki-action@v5
+        with:
+          strategy: init