Replace Go API with PocketBase; update docs

Remove the old Go/Mongo API (api/main.go, go.mod, go.sum, .env.example) and switch telemetry backend to PocketBase (http://db.community-scripts.org). Update documentation and flowcharts to reflect the PocketBase collection (_dev_telemetry_data), new REST endpoints (POST/PATCH/GET), field schema, and revised api.func integration (LXC/VM reporting and status updates). Misc scripts and helpers were adjusted (misc/api.func, misc/build.func, misc/error_handler.func) and a new misc/ingest.go was added. This consolidates telemetry to a hosted PocketBase instance and updates docs and integration points accordingly.

Author: MickLesk