fix(backup): restore from Docker, fail-fast on shadowed /app, bundle encryption key (#1193) (#1197)

* fix(backup): restore uploads through symlinked dir and bundle encryption key (#1193)

Restoring a backup inside Docker threw ERR_FS_CP_DIR_TO_NON_DIR because
/app/server/uploads is a symlink to the mounted /app/uploads volume and
cpSync (dereference:false) refuses to overwrite the symlink node with a
directory. The DB was swapped before this failing copy, so users saw
restored data but missing upload files (trip covers). Resolve the symlink
with realpathSync before copying so the merge targets the real directory;
no-op on a plain dir, so non-Docker behavior is unchanged.

Also bundle the at-rest encryption key (data/.encryption_key) into the
backup so a restore onto a different install can decrypt stored secrets
(API keys, MFA, SMTP/OIDC). Skipped when ENCRYPTION_KEY is provided via
env (the file is not the source of truth then). On restore the key is
swapped back if the archive carries one; a restart is required for the
in-memory key to take effect.

* fix(docker): fail fast when a volume shadows /app (#1193)

Mounting an old volume at /app hides the image's node_modules and dist,
so startup crashed with a cryptic "Cannot find module
'tsconfig-paths/register'". Add a CMD preflight that detects the missing
app files and exits with actionable guidance. Document in the README that
only /app/data and /app/uploads should be mounted, never /app.

* fix: ssrf test

Dockerfile

@@ -105,5 +105,8 @@ HEALTHCHECK --interval=30s --timeout=5s --start-period=15s --retries=3 \
   CMD wget -qO- http://localhost:3000/api/health || exit 1
 
 ENTRYPOINT ["dumb-init", "--"]
+# Preflight: if the app code is missing, a volume was almost certainly mounted
+# over /app (it hides the image's node_modules + dist). Fail with actionable
+# guidance instead of a cryptic "Cannot find module 'tsconfig-paths/register'".
 # cd into server/ so tsconfig-paths/register finds tsconfig.json and ../node_modules resolves correctly.
-CMD ["sh", "-c", "chown -R node:node /app/data /app/uploads 2>/dev/null || true; cd /app/server && exec gosu node node --require tsconfig-paths/register dist/index.js"]
+CMD ["sh", "-c", "if [ ! -f /app/server/dist/index.js ] || [ ! -d /app/node_modules/tsconfig-paths ]; then echo 'FATAL: TREK application files are missing from the image.'; echo 'A volume is likely mounted over /app, which hides the app code.'; echo 'Mount ONLY your data and uploads dirs: -v ./data:/app/data -v ./uploads:/app/uploads'; echo 'Do NOT mount a volume at /app. See the Troubleshooting section of the README.'; exit 1; fi; chown -R node:node /app/data /app/uploads 2>/dev/null || true; cd /app/server && exec gosu node node --require tsconfig-paths/register dist/index.js"]