[IMP] add strict mode (set -euo pipefail) to all scripts

Enable bash strict mode in all shell scripts to catch errors early:
- set -e: Exit immediately if a command exits with non-zero status
- set -u: Treat unset variables as an error
- set -o pipefail: Return value of a pipeline is the status of the last
  command to exit with non-zero status

This prevents silent failures and makes debugging easier by failing fast
when something goes wrong instead of continuing with potentially corrupted
state.

15.0/post_upgrade.sh

@@ -1,4 +1,5 @@
 #!/bin/bash
+set -euo pipefail
 
 echo "Post migration to 15.0..."
 

15.0/pre_upgrade.sh

@@ -1,4 +1,5 @@
 #!/bin/bash
+set -euo pipefail
 
 echo "Prepare migration to 15.0..."
 

15.0/upgrade.sh

@@ -1,3 +1,4 @@
 #!/bin/bash
+set -euo pipefail
 
 compose -f ../compose.yml run -p 8015:8069 ou15 --config=/opt/odoo/auto/odoo.conf --stop-after-init -u all --workers 0 --log-level=debug --max-cron-threads=0 --limit-time-real=10000 --database=ou15 --load=base,web,openupgrade_framework