geolocation: add AddParentDevice and RemoveParentDevice instructions

[nikw9944]

Resolves: #2952

Summary of Changes

• Add AddParentDevice instruction that validates a device is activated in the Serviceability Program before adding it to a GeoProbe's parent_devices list (foundation-gated)
• Add RemoveParentDevice instruction that removes a device pubkey from parent_devices by args (no device account validation needed — device may already be deactivated)
• AddParentDevice is a unit variant (no args) per CLAUDE.md convention — device pubkey is taken directly from the passed account. RemoveParentDevice takes RemoveParentDeviceArgs { device_pk } since no device account is passed

Diff Breakdown

Category	Files	Lines (+/-)	Net
Core logic	4	+152 / -1	+151
Scaffolding	1	+2 / -0	+2
Tests	1	+16 / -1	+15

Compact PR — all new code is core instruction logic with minimal scaffolding

Key files (click to expand)

• smartcontract/programs/doublezero-geolocation/src/processors/geo_probe/add_parent_device.rs — new processor: foundation allowlist check, device ownership + activation validation via Serviceability CPI, duplicate detection, push + realloc via try_acc_write
• smartcontract/programs/doublezero-geolocation/src/processors/geo_probe/remove_parent_device.rs — new processor: foundation allowlist check, not-found detection, retain-based removal + realloc via try_acc_write
• smartcontract/programs/doublezero-geolocation/src/instructions.rs — add AddParentDevice and RemoveParentDevice enum variants + roundtrip test cases
• smartcontract/programs/doublezero-geolocation/src/error.rs — add ParentDeviceAlreadyExists (7) and ParentDeviceNotFound (8) error variants
• smartcontract/programs/doublezero-geolocation/src/entrypoint.rs — wire up two new match arms

Testing Verification

• All 40 unit tests pass including new instruction roundtrip tests for both variants
• 3 integration tests pass (ProgramConfig update scenarios)
• Clippy clean with -Dclippy::all -Dwarnings
• MAX_PARENT_DEVICES (5) enforcement is covered by existing GeoProbe::validate() tests and enforced at write time via try_acc_write
• Related RFC: rfcs/rfc16-geolocation-verification.md