Add serviceName and securitycontext to ltb-passwd,phpldapadmin

[C4tWithShell]

What this PR does / why we need it:

serviceAccountName: {{ .Values.serviceAccountName }}
✅ What it solves:

1. Allows assigning a custom service account.
2. Useful for RBAC-controlled environments
3. Avoids using the default service account which may be over-privileged.
4. Enables least-privilege principles.

securityContext with .Values.podSecurityContext
✅ What it solves:

1. Enables secure defaults like running as non-root, dropping capabilities, setting fsGroup, etc.

Container-level securityContext
✅ What it solves:

1. Same pattern as podSecurityContext, but for individual containers.
2. Enforces things like readOnlyRootFilesystem, runAsNonRoot, drop: [ALL] per container.

Pre-submission checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you updated the readme?
• Is this PR backward compatible? If it is not backward compatible, please discuss open a ticket first