feat: add missing redis-backed collectors

[rokernel]

Summary

• add Redis-backed collectors for routing, switch, thermal, transceiver, and platform health data
• extend the LLDP collector with local chassis metadata from LLDP_LOC_CHASSIS
• add fixture-driven tests and README updates for the new collectors and toggles

Why

These Redis families were present on the switch but not exported yet, while duplicate coverage for existing VLAN/LAG/FDB/state-copy metrics was intentionally skipped.

Testing

• go test ./...
• go build ./...
• ./scripts/build.sh
• docker compose up --build -d
• docker compose ps
• docker compose down

Notes

• routing and platform health stay opt-in to control cardinality and runtime cost
• unrelated dashboard changes in the working tree were intentionally left out of this PR