chore(migrations): renumber 108_add_backup_paths to 109 to avoid upstream collision

upstream/beta independently shipped 108_seed_sl_email_template_translations.js
(Slovenian email template translations) using the migration number
this branch had already claimed for 108_add_backup_paths.js. Knex's
filename-based ordering would have caused both to attempt the slot
at merge time.

Renamed via `git mv` so file history is preserved. All five
references updated in lockstep:
  - backend/src/services/_backupPathsBoot.js (require + comments)
  - backend/src/services/backupService.js (LEGACY_BACKUP_PATHS comment)
  - 3 integration test files (require + "migration 108" prose)
  - migration's own header comment, with a paragraph explaining the
    rename so reviewers don't wonder why the number jumped

**No data-migration impact for installs that already ran the
108-named version** (Ralf's beta, primarily): the migration's body
is idempotent — createTable is guarded by `hasTable`, and the seed
uses `onConflict('path').ignore()`. So when 109 runs against an
install whose backup_paths table is already populated, both the
schema step and the seed step no-op cleanly. The orphaned
`108_add_backup_paths.js` row in the `migrations` tracking table
sits harmlessly alongside the new `109_add_backup_paths.js` row.

No data lost, no double-insert, no schema drift. Mechanical rename
ahead of the PR opening.

backend/src/services/_backupPathsBoot.js

@@ -4,7 +4,7 @@
  * **Why this exists**
  *
  * Knex won't re-run an applied migration, so once migration
- * 108_add_backup_paths.js has run, any later default we want to add
+ * 109_add_backup_paths.js has run, any later default we want to add
  * (a new subdirectory shipped by a future feature) would never reach
  * already-deployed installs. The historical fix for this kind of
  * "schema is fine, seed drifted" problem is the boot-time self-heal
@@ -14,7 +14,7 @@
  *
  * **Authoritative list**
  *
- * The list of defaults lives on migration 108 itself
+ * The list of defaults lives on migration 109 itself
  * (`DEFAULT_PATHS` export) — one source of truth that both the
  * migration and this seeder read. Tests assert these two stay in
  * lockstep.
@@ -22,14 +22,14 @@
  * **Failure semantics**
  *
  * If the table doesn't exist yet (migrations haven't run, fresh
- * install before migration 108 lands, etc.) we no-op and log. The
+ * install before migration 109 lands, etc.) we no-op and log. The
  * walker has a hard-coded `LEGACY_DEFAULTS` fallback for the same
  * reason — defense in depth so "Run Backup Now" can never silently
  * ship a files-only manifest because of a seed issue. See
  * `backupService.js` getFilesToBackupInternal.
  */
 
-const { DEFAULT_PATHS } = require('../../migrations/core/108_add_backup_paths');
+const { DEFAULT_PATHS } = require('../../migrations/core/109_add_backup_paths');
 
 let booted = false;
 
@@ -45,7 +45,7 @@ async function seedBackupPathsAtBoot(db, logger) {
   if (booted) return { seeded: [] };
 
   if (!(await db.schema.hasTable('backup_paths'))) {
-    log.warn('backup_paths table missing at boot — self-heal skipped (migration 108 may not have run yet)');
+    log.warn('backup_paths table missing at boot — self-heal skipped (migration 109 may not have run yet)');
     return { seeded: [] };
   }
 

backend/src/services/backupService.js

@@ -419,7 +419,7 @@ async function scanDirectory(dirPath, fileList, basePath, excludePatterns = [])
 
 /**
  * Hard-coded fallback when `backup_paths` is missing/empty. Mirrors
- * the canonical seed in migration 108 — kept here as defense in depth
+ * the canonical seed in migration 109 — kept here as defense in depth
  * so the walker can never silently degrade to "no directories scanned"
  * because of a seed problem.
  *