feat: harden pipeline UX — preprocess, rembg alpha, remix/lightbox

Downscale to 2000px JPEG before rembg, random blend opacity, timeout
retries, per-variant remix prefill, lightbox, and longer SFTP idle.

Co-authored-by: Cursor <cursoragent@cursor.com>

compose.yml

@@ -22,6 +22,9 @@ services:
     environment:
       SFTP_USER: ${SFTP_USER:-livef12}
       SFTP_PASSWORD: ${SFTP_PASSWORD:-changeme}
+      # Minutes. Default SFTPGo is 15 — too aggressive for Android clients
+      # that idle after a successful upload (shows up as EOF in the logs).
+      SFTPGO_COMMON__IDLE_TIMEOUT: ${SFTPGO_IDLE_TIMEOUT:-120}
     volumes:
       - ${DATA_HOST_DIR:-./data}:/srv/sftpgo/data
       - sftpgo_state:/var/lib/sftpgo
@@ -47,8 +50,14 @@ services:
       DATA_DIR: /data
       OUTPUT_COUNT: ${OUTPUT_COUNT:-3}
       BLEND_OPACITY: ${BLEND_OPACITY:-30%}
+      BLEND_OPACITY_MIN: ${BLEND_OPACITY_MIN:-10}
+      BLEND_OPACITY_MAX: ${BLEND_OPACITY_MAX:-50}
       FILTER_TIMEOUT: ${FILTER_TIMEOUT:-120}
+      FILTER_TIMEOUT_LONG: ${FILTER_TIMEOUT_LONG:-300}
       MAX_FILTER_ATTEMPTS: ${MAX_FILTER_ATTEMPTS:-8}
+      MAX_EDGE_PX: ${MAX_EDGE_PX:-2000}
+      REMBG_MODEL: ${REMBG_MODEL:-u2net}
+      REMBG_ALPHA: ${REMBG_ALPHA:-1}
       NICE_LEVEL: ${NICE_LEVEL:-18}
     volumes:
       - ${DATA_HOST_DIR:-./data}:/data
@@ -56,8 +65,9 @@ services:
       - rembg_cache:/app/.home
     # Sequential-only by design (no threads/async in worker.py); these
     # limits just make sure gmic/rembg can't starve the host too.
+    # Keep headroom on the ~8GB host — birefnet-general needs more than we have.
     cpus: "1.0"
-    mem_limit: 2g
+    mem_limit: 4g
     networks:
       - internal
 
@@ -71,8 +81,14 @@ services:
       DATA_DIR: /data
       OUTPUT_COUNT: ${OUTPUT_COUNT:-3}
       BLEND_OPACITY: ${BLEND_OPACITY:-30%}
+      BLEND_OPACITY_MIN: ${BLEND_OPACITY_MIN:-10}
+      BLEND_OPACITY_MAX: ${BLEND_OPACITY_MAX:-50}
       FILTER_TIMEOUT: ${FILTER_TIMEOUT:-120}
+      FILTER_TIMEOUT_LONG: ${FILTER_TIMEOUT_LONG:-300}
       MAX_FILTER_ATTEMPTS: ${MAX_FILTER_ATTEMPTS:-8}
+      MAX_EDGE_PX: ${MAX_EDGE_PX:-2000}
+      REMBG_MODEL: ${REMBG_MODEL:-u2net}
+      REMBG_ALPHA: ${REMBG_ALPHA:-1}
       NICE_LEVEL: ${NICE_LEVEL:-18}
       SITE_TITLE: live.f12.rocks
     volumes: