fix: Remove global LD_LIBRARY_PATH to restore SSL certificate verification for email

Fixes SSL certificate verification failure when sending books to Kindle via email.
Users were getting "[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed:
unable to get local issuer certificate (_ssl.c:1032)" errors after recent updates.

Root Cause:
Commit 8638224 (feat: FTS management) added global LD_LIBRARY_PATH=/app/calibre/lib
environment variable to force Calibre binaries to use their bundled libraries for
FTS functionality. However, setting this globally caused Python's SSL/TLS module to
load SSL libraries from Calibre's bundle instead of system OpenSSL, breaking cert
verification for SMTP connections.

Changes:
- Removed `ENV LD_LIBRARY_PATH=/app/calibre/lib` from Dockerfile
- Removed `export LD_LIBRARY_PATH=/app/calibre/lib` from s6 service run script
- Kept per-subprocess LD_LIBRARY_PATH settings in cps/cwa_functions.py (lines 2083,
  2151, 2198, 2274) which correctly isolate the variable to calibredb calls only

Impact:
- Email/SMTP functionality restored with proper SSL verification
- FTS and all Calibre tool operations continue working correctly via subprocess env
- No side effects on other functionality

Reported by user on Discord who found issue present in dev branch but not in
dev-auto-hardcover image (commit 297968d).

Author: crocodilestick

Dockerfile

@@ -286,7 +286,6 @@ COPY --from=unrar /usr/bin/unrar-ubuntu /usr/bin/unrar
 
 # Set calibre environment variables
 ENV CALIBRE_CONFIG_DIR=/config/.config/calibre
-ENV LD_LIBRARY_PATH=/app/calibre/lib
 
 # Ports and volumes
 WORKDIR /config

root/etc/s6-overlay/s6-rc.d/svc-calibre-web-automated/run

@@ -2,7 +2,6 @@
 # shellcheck shell=bash
 
 export CALIBRE_DBPATH=/config
-export LD_LIBRARY_PATH=/app/calibre/lib
 
 exec \
     s6-notifyoncheck -d -n 300 -w 1000 -c "nc -z localhost ${CWA_PORT_OVERRIDE:-8083}" \