[feat] Add frontend VPC support for NodeBalancers

[komer3]

Add support for configuring NodeBalancer frontend VPC placement via service annotations. This enables NodeBalancers to be deployed with private frontend addresses within a VPC.

New annotations:

• linode-loadbalancer-frontend-ipv4-range: Explicit IPv4 CIDR
• linode-loadbalancer-frontend-ipv6-range: Explicit IPv6 CIDR
• linode-loadbalancer-frontend-vpc-name: VPC name for resolution
• linode-loadbalancer-frontend-subnet-name: Subnet name for resolution
• linode-loadbalancer-frontend-subnet-id: Direct subnet ID

Resolution precedence:

1. IPv4/IPv6 Range annotations (explicit CIDR)
2. VPC/Subnet name annotations (name-based resolution)
3. Subnet ID annotation (direct ID)

Key behavioral difference from backend VPC implementation:

• Frontend VPC is opt-in: returns nil when no annotations are present, resulting in no frontend VPC configuration
• Backend VPC is always configured: falls through precedence levels and always returns VPC options using the service's default subnet ID

This design allows frontend VPC to remain an optional feature while backend VPC continues to be mandatory for NodeBalancer operation.

Includes:

• CIDR validation for IPv4 and IPv6 ranges
• Name-to-ID resolution requiring both vpc-name and subnet-name
• Unit tests for validation, status generation, and option building
• Debug logging for frontend VPC NodeBalancers

General:

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