Fix audited protocol, inventory, and admin features

[ANONYMOUSZED-beep]

Summary

• make Play packet dispatch protocol-safe and preserve exact negotiated protocol IDs
• fix Login Success serialization across 1.8 through 1.21.4 and generate vanilla-compatible offline UUIDs
• enforce configured protocol allowlists and reject unsupported protocols instead of silently downgrading
• implement authoritative basic inventory clicks with correct window-slot mapping
• prevent dropped-item loss, preserve partial pickup remainders, and restore persisted inventory/NBT data
• restore Python mod enable/event/tick/shutdown lifecycle wiring
• broadcast fluid changes, encode falling fluid correctly, and tick furnace containers
• validate KeepAlive responses/timeouts and expose loopback Watchdog health responses
• secure Web Admin with loopback-only defaults unless remote access is explicitly enabled
• run tests on Linux, macOS, and Windows CI jobs and package staged native components
• audit README claims so partial and unsupported features are no longer marked complete

Validation

• python -m pytest -q — 45 passed
• python -m compileall -q .
• git diff --check
• clean working tree; PR head verified at d070fef77ffc715dcb5b047524cf5bd5fef931de

CI note

GitHub currently reports action_required with zero jobs because this is a first-time fork pull request. A maintainer must approve workflow execution. No CI job has failed.

Local native CMake compilation could not be run because CMake is unavailable in the local environment; the workflow builds and stages native targets on Linux, macOS, and Windows.