feat: add VitePress docs site, music file picker modal, Dockerfile optimization, i18n keys for 14 locales

- Add docs/ with VitePress site (19 pages): guide, config, architecture, FAQ
- Add GitHub Actions workflow for auto-deploy to GitHub Pages
- Replace music 'Add Tracks' upload picker with in-app audio file browser modal
- Add music picker CSS styles with dark theme support
- Add missing i18n keys (search_audio, no_audio_files, etc.) to all 14 locales
- Optimize Dockerfile: shared base stage, COPY --chmod, consolidated RUN, HEALTHCHECK
- Improve README: docs links, updated stats (222+ tests, 14 languages), feature status

Dockerfile

@@ -1,8 +1,11 @@
-# Stage 1: Cache dependencies
-FROM rust:1.94.0-alpine3.23 AS cacher
-WORKDIR /app
+# ─── Stage 1: Shared build base (avoids duplicate apk install) ────────────────
+FROM rust:1.94.1-alpine3.23 AS base
 RUN apk --no-cache upgrade && \
     apk add --no-cache musl-dev pkgconfig postgresql-dev gcc perl make
+
+# ─── Stage 2: Cache dependencies ─────────────────────────────────────────────
+FROM base AS cacher
+WORKDIR /app
 COPY Cargo.toml Cargo.lock ./
 # build.rs + static/ are needed so the build script can run and set OUT_DIR
 COPY build.rs ./
@@ -13,11 +16,10 @@ RUN mkdir -p src/bin && \
     echo 'fn main() {}' > src/bin/generate-openapi.rs && \
     cargo build --release && \
     rm -rf src static-dist target/release/deps/oxicloud* target/release/build/oxicloud-*
-# Stage 2: Build the application
-FROM rust:1.94.0-alpine3.23 AS builder
+
+# ─── Stage 3: Build the application ──────────────────────────────────────────
+FROM base AS builder
 WORKDIR /app
-RUN apk --no-cache upgrade && \
-    apk add --no-cache musl-dev pkgconfig postgresql-dev gcc perl make
 # Copy cached dependencies (only target dir and cargo registry)
 COPY --from=cacher /app/target target
 COPY --from=cacher /usr/local/cargo/registry /usr/local/cargo/registry
@@ -30,7 +32,7 @@ COPY migrations migrations
 ARG DATABASE_URL="postgres://postgres:postgres@localhost/oxicloud"
 RUN DATABASE_URL="${DATABASE_URL}" cargo build --release
 
-# Stage 3: Create minimal final image
+# ─── Stage 4: Minimal runtime image ──────────────────────────────────────────
 FROM alpine:3.23.3
 
 # OCI image metadata
@@ -44,19 +46,13 @@ LABEL org.opencontainers.image.title="OxiCloud" \
 # 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 su-exec
-
-# Create non-root user
-RUN addgroup -g 1001 -S oxicloud && \
+    apk add --no-cache libgcc ca-certificates libpq tzdata su-exec && \
+    addgroup -g 1001 -S oxicloud && \
     adduser -u 1001 -S oxicloud -G oxicloud
 
-# Copy only the compiled binary
-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 the compiled binary and entrypoint (--chmod avoids extra RUN chmod layers)
+COPY --from=builder --chmod=755 /app/target/release/oxicloud /usr/local/bin/
+COPY --chmod=755 entrypoint.sh /usr/local/bin/entrypoint.sh
 
 # Copy processed static files (bundled/minified by build.rs in release)
 COPY --from=builder --chown=oxicloud:oxicloud /app/static-dist /app/static
@@ -69,6 +65,11 @@ WORKDIR /app
 # Expose application port
 EXPOSE 8086
 
+# Basic health check — verifies the HTTP server responds on the main port.
+# Docker / Compose / Swarm will mark the container unhealthy after 3 failures.
+HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
+    CMD wget -qO- http://localhost:8086/api/version || exit 1
+
 # 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.