fix: resolve Docker volume permission denied on startup

Root cause: Docker named volumes are created as root, but the container
ran as the unprivileged 'oxicloud' user (UID 1001). Services like
thumbnail_service, image_transcode, and dedup_service call
create_dir_all under /app/storage during initialization, which fails
with 'Permission denied (os error 13)'.

Changes:
- Add entrypoint.sh that runs as root to chown /app/storage, then
  drops privileges via su-exec before executing the application
- Update Dockerfile to install su-exec, copy entrypoint, and use
  ENTRYPOINT instead of USER+CMD
- Downgrade id_mapping_service initial write failure from ERROR to WARN
  (empty in-memory map is perfectly valid, will persist on next save)
- Improve panic message in main.rs to hint at Docker permission issue

Fixes #<issue>

Dockerfile

@@ -37,8 +37,9 @@ LABEL org.opencontainers.image.title="OxiCloud" \
       org.opencontainers.image.licenses="MIT"
 
 # Install only necessary runtime dependencies and update packages
+# su-exec is needed by the entrypoint to drop privileges after fixing volume permissions
 RUN apk --no-cache upgrade && \
-    apk add --no-cache libgcc ca-certificates libpq tzdata
+    apk add --no-cache libgcc ca-certificates libpq tzdata su-exec
 
 # Create non-root user
 RUN addgroup -g 1001 -S oxicloud && \
@@ -48,12 +49,16 @@ RUN addgroup -g 1001 -S oxicloud && \
 COPY --from=builder /app/target/release/oxicloud /usr/local/bin/
 RUN chmod +x /usr/local/bin/oxicloud
 
+# Copy entrypoint script
+COPY entrypoint.sh /usr/local/bin/entrypoint.sh
+RUN chmod +x /usr/local/bin/entrypoint.sh
+
 # Copy static files and other resources needed at runtime
 COPY --chown=oxicloud:oxicloud static /app/static
 COPY --chown=oxicloud:oxicloud db /app/db
 
 # Create storage directory with proper permissions
-RUN mkdir -p /app/storage && chown oxicloud:oxicloud /app/storage
+RUN mkdir -p /app/storage && chown -R oxicloud:oxicloud /app/storage
 
 # Set working directory
 WORKDIR /app
@@ -61,8 +66,8 @@ WORKDIR /app
 # Expose application port
 EXPOSE 8086
 
-# Run as non-root user
-USER oxicloud
-
-# Run the application
+# Entrypoint fixes volume permissions then drops to oxicloud user.
+# The container starts as root so it can chown mounted volumes,
+# then su-exec drops privileges before running the application.
+ENTRYPOINT ["entrypoint.sh"]
 CMD ["oxicloud"]

entrypoint.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+set -e
+
+# Fix ownership of mounted volumes.
+# When Docker creates named volumes they are owned by root, but the
+# application runs as the unprivileged "oxicloud" user (UID 1001).
+# This script runs as root, fixes permissions, then drops privileges.
+
+STORAGE_DIR="/app/storage"
+STATIC_DIR="/app/static"
+
+# Ensure the storage directory exists and is writable by oxicloud
+if [ -d "$STORAGE_DIR" ]; then
+    chown -R oxicloud:oxicloud "$STORAGE_DIR"
+fi
+
+# Ensure static directory is readable
+if [ -d "$STATIC_DIR" ]; then
+    chown -R oxicloud:oxicloud "$STATIC_DIR"
+fi
+
+# Drop privileges and exec the main binary (or whatever was passed as CMD)
+exec su-exec oxicloud "$@"

src/infrastructure/services/id_mapping_service.rs

@@ -181,11 +181,11 @@ impl IdMappingService {
             }
         }
         
-        // Write empty map to file
+        // Write empty map to file (best-effort: the in-memory map is valid even if disk write fails)
         match serde_json::to_string_pretty(&empty_map) {
             Ok(json) => {
                 if let Err(e) = fs::write(map_path, json).await {
-                    tracing::error!("Failed to write initial empty ID map: {}", e);
+                    tracing::warn!("Could not write initial empty ID map (will retry on next save): {}", e);
                 } else {
                     tracing::info!("Created initial empty ID map at {}", map_path.display());
                 }

src/main.rs

@@ -85,7 +85,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     );
     
     let app_state = factory.build_app_state(db_pool).await
-        .expect("Failed to build application state");
+        .expect("Failed to build application state. If running in Docker, ensure the storage volume is writable by the oxicloud user (UID 1001)");
 
     // Build application router
     let api_routes = create_api_routes(&app_state);