docs(geolocation): Add Geolocation Sidecar Architecture and sensor hardware attestation

- Add Geolocation Sidecar Architecture section with three sensor modes:
  * Mode 1: GNSS (local sensor, optionally HW-signed)
  * Mode 2.1: Mobile Network via CAMARA (direct location retrieval)
  * Mode 2.2: Mobile Network via CAMARA (boundary verify - future extension)
- Add GNSS Trust Tiers (Tier 1: HW-signed, Tier 2: consumer)
- Add Sensor Hardware Attestation section for anti-swap protection
  * Explains how sensor_imei/sensor_serial_number in PCR 15 prevents rogue sensor swaps
- Update ZKP circuit to support optional GNSS hardware signatures
- Replace generic TPM flow with mode-specific TPM-attested ZKP flows
- Clarify sidecar (location + ZKP) vs agent (TPM operations) responsibilities
- Update Multi-Sensor Fusion section to reference sidecar architecture
- Renumber sections 4-9 to 5-10 after new content additions

Author: ramkri123