Add IoT telemetry analysis and history tools

[ShuxinLin]

Summary

• Add the IoT stream_extent, history, latest_reading, sensor_coverage, and sensor_stats MCP tools.
• Parse ISO 8601 timestamps consistently, apply half-open windows by chronological value, compare aware timestamps by instant, and reject invalid or mixed-awareness streams.
• Add exact paged history with query-bound opaque cursors, sensor projection, metadata exclusion, and final-page lookahead.
• Select latest readings by parsed timestamp and report UTC age with explicit offset-free timestamp semantics.
• Compute full-stream sensor coverage and constant-memory numeric statistics with explicit handling for missing, null, invalid, and non-finite values.
• Keep decorated tool functions in main.py, move response models to models.py, and centralize telemetry timestamp, paging, projection, cursor, and accumulator logic in telemetry_helper.py.
• Review and tighten all 12 IoT tool docstrings, shorten the server instruction to routing guidance, and document the complete registry and telemetry tool surface.
• Keep generated tool descriptions and returned errors storage-neutral.

Tests

• .venv/bin/pytest src/servers/iot/tests (90 passed)
• .venv/bin/python -m py_compile src/servers/iot/main.py src/servers/iot/models.py src/servers/iot/telemetry_helper.py src/servers/iot/tests/test_tools.py
• Live smoke tests for full-range, date-only, sensor-filtered, all-sensor, invalid-sensor, timezone-mismatch, full sensor coverage, two-page history, exact final-page detection, and latest readings.

This branch was created from add-iot-measured-sensors; that branch has since merged into main in #450, so this PR targets main.

[DhavalRepo18]

Repeatng one more time, I am merging this PR so we can all look at the all tools in one place and arrangement become easy.