replace Redis with an embedded SQLite string->string KV store (group commit, in-tx events, SQL search)

Dockerfile

@@ -6,20 +6,20 @@
 # - Bash-based leader election script (flock on shared volume)
 # - meta-core Go binary (HTTP API, Mount API, Watcher)
 # - nginx (dashboard, WebDAV, API proxy)
-# - Redis (managed by supervisord on leader)
+# - SQLite metadata store, embedded in the Go binary (/meta-core/db/meta-core.db)
 # - rclone (single mount executor — SMB goes through rclone's :smb: backend)
 # - supervisord (process management - runs on leader only)
 #
 # Architecture:
 # - leader-election.sh handles flock, starts supervisord on leader
 # - Followers remain dormant, retry flock every 5s
-# - Only leader runs Redis, meta-core, nginx, rclone, mount-watcher
+# - Only leader runs meta-core, nginx, rclone, mount-watcher
 # =============================================================================
 
 # -----------------------------------------------------------------------------
 # Stage 1: Build Go binary
 # -----------------------------------------------------------------------------
-FROM golang:1.21-alpine AS go-builder
+FROM golang:1.26-alpine AS go-builder
 
 RUN apk add --no-cache git
 
@@ -74,7 +74,7 @@ ARG RCLONE_VERSION=1.73.5
 # Install runtime dependencies. Native NFS/CIFS clients intentionally absent —
 # all remote mounts go through rclone now.
 RUN apk add --no-cache \
-    redis \
+    sqlite \
     nginx \
     nginx-mod-http-dav-ext \
     supervisor \
@@ -104,7 +104,7 @@ RUN chmod +x /usr/local/bin/meta-core
 # Create directories
 RUN mkdir -p \
     /meta-core/locks \
-    /meta-core/db/redis \
+    /meta-core/db \
     /meta-core/services \
     /meta-core/mounts/errors \
     /files \
@@ -140,13 +140,12 @@ ENV META_CORE_PATH=/meta-core \
     SERVICE_VERSION=1.0.0 \
     META_CORE_HTTP_PORT=9000 \
     META_CORE_HTTP_HOST=0.0.0.0 \
-    REDIS_PORT=6379 \
     WATCH_INTERVAL_MS=1000
 
 # Expose ports
-# 80: nginx (dashboard + API proxy + WebDAV)
-# 6379: Redis (for other services)
-EXPOSE 80 6379
+# 80: nginx (dashboard + API proxy + WebDAV). The metadata store has no port:
+# it is a file inside this container, reachable only through the HTTP API.
+EXPOSE 80
 
 # Health check
 HEALTHCHECK --interval=10s --timeout=5s --start-period=10s --retries=3 \