feat: slskd reconnect guard in downloaders_reset, mass v2 sync

- downloaders_reset: connection check block before slskd API sections;
  triggers PUT /api/v0/server reconnect if disconnected, polls 60s,
  gates Stuck Searches and Dead Transfer Records on SLSKD_CONNECTED
- Sync all modified/new/deleted files from v2 refactor across Docker_Essentials,
  Media, Monitors, Partnership, Rsync, Tools, Transcodes, unRAID_Essentials,
  common.sh, master confs, and new Manual/README docs

Monitors/backup_verify.sh

@@ -1,49 +1,103 @@
 #!/bin/bash
 # ==============================================================================================
-# ================================= Backup Verify ==============================================
+# ============================= Backup Verify ==================================================
 # ==============================================================================================
-# Verifies the rsync mirror is healthy by comparing random file samples between
-# local and remote servers using MD5 checksums.
 #
-# ── WHAT IT DOES ──────────────────────────────────────────────────────────────────────────────
-# Randomly samples BACKUP_VERIFY_SAMPLE files per share above BACKUP_VERIFY_MIN_SIZE,
-# computes MD5 checksums locally, then computes the same checksums on the remote via SSH
-# and compares results. Catches silent corruption or incomplete syncs that rsync itself
-# would not detect.
+# PURPOSE
+# ─────────────────────────────────────────────────────────────────────────────
+# rsync mirror integrity verification via independent MD5 checksums. Scheduled
+# weekly (Sunday 10am). Randomly samples BACKUP_VERIFY_SAMPLE files per share
+# above BACKUP_VERIFY_MIN_SIZE, computes checksums locally, then computes the
+# same checksums on the remote via SSH and compares.
 #
-# ── RESULTS PER FILE ──────────────────────────────────────────────────────────────────────────
-#   MATCH   — checksums identical, file is correctly mirrored ✅
-#   MISMATCH — file exists on both but checksums differ — sync may have partially failed
-#   MISSING  — file exists locally but not on remote — not yet synced or deleted on remote
+# Per file: MATCH (checksums identical) | MISMATCH (file exists on both but
+# checksums differ — sync failure or corruption) | MISSING (file exists locally
+# but not on remote). All MISMATCHes and significant MISSINGs trigger notification.
+# rsync exit code 0 is not trusted — this script verifies actual content.
 #
-# ── SHARE SELECTION ───────────────────────────────────────────────────────────────────────────
-# Uses HOST*_BACKUP_VERIFY_SHARES if defined, falls back to HOST*_DAILY_SYNC_SHARES.
-# Both aliased by detect_hosts() — no manual HOST1/HOST2 selection needed.
+# Share list from HOST*_BACKUP_VERIFY_SHARES if defined, otherwise falls back
+# to HOST*_DAILY_SYNC_SHARES. Both aliased by detect_hosts().
 #
-# ── SAFEGUARDS ────────────────────────────────────────────────────────────────────────────────
-#   acquire_lock         — prevents concurrent runs producing duplicate/conflicting results
-#   check_connectivity() — verifies remote reachable before attempting SSH calls
-#   check_remote_array() — verifies remote array mounted before checksums
-#                          remote array down = all files "missing" = false alarm ✅
-#   version parity       — verifies both servers on compatible unRAID before trusting results
-#   SSH_TIMEOUT          — all SSH calls protected against hangs
-#   validate_unraid_cmd  — notify script validated before use
-#   Silent by default    — only issues produce output, all-match runs are silent
+# ==============================================================================================
+# DESIGN PRINCIPLES
+# ==============================================================================================
 #
-# ── CONFIGURATION (master_host*.conf) ─────────────────────────────────────────────────────────
-#   HOST*_BACKUP_VERIFY_SHARES — override share list (empty = use DAILY_SYNC_SHARES)
-#   HOST*_DAILY_SYNC_SHARES    — fallback share list
-#   All aliased by detect_hosts()
+# Independent Verification
+#   rsync reports success when the transfer completed without network errors and
+#   file sizes and modification times match. It does not detect silent corruption
+#   during transfer (bitflip in transit), corruption written to storage at rest
+#   (faulty drive sector), or files that matched size/mtime but had wrong content.
+#   All of these produce exit code 0. This script checks whether "done" means "correct."
 #
-# ── CONFIGURATION (master.conf) ───────────────────────────────────────────────────────────────
-#   BACKUP_VERIFY_SAMPLE   — random files to check per share (default 10)
-#   BACKUP_VERIFY_MIN_SIZE — minimum file size to include in sample (default 1M)
+# Intentionally Small Sample
+#   10 files per share (default) — a spot check, not an exhaustive verify.
+#   Catches systematic problems and hardware issues while running in minutes, not
+#   hours. Full verification would take longer than the rsync itself.
+#
+# ==============================================================================================
+# OPERATIONAL SAFEGUARDS
+# ==============================================================================================
+#
+# Single Instance Lock
+#   acquire_lock prevents concurrent runs producing conflicting results.
+#
+# Remote Connectivity Check
+#   check_connectivity() verifies the remote Tailscale IP is reachable before
+#   any SSH calls. Without this, all files show as MISSING on a network hiccup.
+#
+# Remote Array Check
+#   check_remote_array() verifies /mnt/user is mounted on the remote before
+#   computing checksums. Array not started = all files "missing" = false alarm.
+#
+# Version Parity
+#   Refuses to run if remote unRAID version doesn't match local. A mismatch
+#   may mean the remote is in an unexpected state.
+#
+# SSH Timeout
+#   SSH_TIMEOUT caps all SSH calls. One hung connection does not block the run.
+#
+# Notification Validated
+#   validate_unraid_cmd confirms the notify script is present before use.
+#
+# ==============================================================================================
+# CONFIGURATION
+# ==============================================================================================
+#
+# master_host*.conf
+#
+#   HOST*_BACKUP_VERIFY_SHARES
+#       Shares to verify. Leave empty to use HOST*_DAILY_SYNC_SHARES automatically.
+#       Aliased by detect_hosts() → BACKUP_VERIFY_SHARES.
+#
+#   HOST*_DAILY_SYNC_SHARES
+#       Fallback share list if BACKUP_VERIFY_SHARES is empty. Aliased by detect_hosts().
+#
+# master.conf
+#
+#   BACKUP_VERIFY_SAMPLE
+#       Random files checked per share per run. (default: 10)
+#
+#   BACKUP_VERIFY_MIN_SIZE
+#       Minimum file size to include in sample — tiny files have low corruption
+#       risk and slow checksums. (default: 1M)
+#
+# ==============================================================================================
+# RUNTIME MODES
+# ==============================================================================================
+#
+# backup_verify.sh
+#     Sample files from all shares and compare checksums. Notify on MISMATCH
+#     or significant MISSING count. Silent when all samples match.
+#
+# backup_verify.sh --dry-run
+#     Show which files would be sampled. No checksums computed, no notifications.
+#
+# backup_verify.sh --status
+#     Show share list, sample size, and min file size configuration. Then exit.
+#
+# backup_verify.sh --log
+#     Verbose per-file checksum comparison output during the run.
 #
-# ── USAGE ─────────────────────────────────────────────────────────────────────────────────────
-#   backup_verify.sh              — normal run
-#   backup_verify.sh --dry-run    — show sample selection only, no checksums
-#   backup_verify.sh --log        — verbose output
-#   backup_verify.sh --status     — show config and exit
 # ==============================================================================================
 
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"