fix: resolve storage healthcheck path via LOCAL_STORAGE_PATH env var (#3004)

* fix: resolve local data directory to /app/data in production Docker

In the official Docker image, cwd is /app/apps/web (set via WORKDIR), but
the data volume is mounted at /app/data. Without pnpm-workspace.yaml present
in the runtime image, findWorkspaceRoot() returns null, so getLocalDataDirectory()
fell back to <cwd>/data = /app/apps/web/data, which the node user has no
permission to create. This caused the storage healthcheck to fail with
EACCES.

Add a production fallback: when cwd ends in apps/web, resolve the data
directory to two levels up (matching /app/data in the official image).

Re-resolves #2990.

https://claude.ai/code/session_015pSTtukxf7mFTty2Y6PHZf

* fix: replace apps/web heuristic with LOCAL_STORAGE_PATH env var

The previous fix special-cased a cwd ending in apps/web to land on /app/data,
but the heuristic could false-positive on any path with that suffix and was
fragile to Dockerfile changes. pnpm-workspace.yaml is never copied into the
runtime image, so the workspace-root walk was also dead code in production.

Replace the heuristic with an explicit LOCAL_STORAGE_PATH env var:
- Set LOCAL_STORAGE_PATH=/app/data in the Dockerfile (single source of truth).
- Add LOCAL_STORAGE_PATH to the env schema; storage and statistics services
  pass it through to getLocalDataDirectory.
- getLocalDataDirectory now uses the override when set, else workspace root
  (dev), else cwd/data.
- New Nitro plugin validates the resolved local data directory at startup
  and refuses to boot with a clear error if it isn't writable, surfacing
  permission issues immediately instead of at first upload/healthcheck.
- Document the new variable in .env.example and the Docker self-hosting docs.

https://claude.ai/code/session_015pSTtukxf7mFTty2Y6PHZf

* fix: address review feedback on storage path handling

- apps/web/plugins/2.storage.ts: use the default-import style for
  node:fs/promises (matches the rest of the repo, sidesteps any
  named-export concerns for fs.constants).
- packages/env/src/server.ts: reject relative LOCAL_STORAGE_PATH values
  via a zod refinement. Relative paths would be resolved against cwd,
  which differs between dev and Docker — exactly the same surprise the
  original bug had. Failing fast at config validation time gives a
  clear error before the server boots.

https://claude.ai/code/session_015pSTtukxf7mFTty2Y6PHZf

* fix: update data volume configuration in Docker Compose and enhance Nitro plugin

* fix: remove "Can I customize the templates?" FAQ entry from multiple language files

---------

Co-authored-by: Claude <noreply@anthropic.com>

docs/self-hosting/docker.mdx

@@ -329,6 +329,7 @@ openssl rand -hex 32
 <Accordion title="Storage (S3 or local)">
   - **Default (local)**: If all `S3_*` values are empty, uploads are stored under `/app/data` in the official image.
   - Mount local uploads to persistent storage (for example `./data:/app/data`) or uploads can be lost on container recreation.
+  - **`LOCAL_STORAGE_PATH`** (optional): Overrides the local data directory. Defaults to `/app/data` in the official Docker image and `<workspace>/data` in development. The container validates this path is writable at startup and refuses to start otherwise.
   - **Rootless Docker**: `/app/data` remains the container path. Prefer the named volume from the example Compose file, or make sure a bind-mounted host directory is writable by the container's `node` user mapping.
   - **S3/S3-compatible**: Configure `S3_ACCESS_KEY_ID`, `S3_SECRET_ACCESS_KEY`, `S3_REGION`, `S3_ENDPOINT`, and `S3_BUCKET`.
   - **`S3_FORCE_PATH_STYLE`** controls bucket addressing (defaults to `"false"`):