feat: pH/EC Regulation v2 — Telegram, daily dose limits, water level safety lock

[m0nk1111]

Summary

Enhanced pH/EC regulation function that replaces/supplements the built-in regulate_ph_ec.py. Designed for hydroponic and aquaponic setups where reliability and safety are critical.

What's New vs Built-in

Feature	Built-in regulate_ph_ec	This v2
pH regulation (raise/lower)	✅	✅
EC regulation (raise/lower)	✅ (2 pumps)	✅ (up to 4 pumps A-D)
Daily dose limits (ml/day)	❌	✅ with midnight reset
Water level safety lock	❌	✅ blocks dosing when dry
Telegram notifications	❌	✅ danger alerts + stale data
In-band dose halving	❌	✅ gentle convergence
InfluxDB dose logging (ml)	❌	✅ channels 0/1/2 for graphs
Sensor sanity checks	❌	✅ stale + flatline detection
Per-pump ml/min calibration	❌	✅ accurate ml calculation
Persistent status widget	❌	✅ function_status_always()
Daily + all-time counters	❌	✅ persisted across restarts
Countdown timer in status	❌	✅

Key Design Decisions

• Non-breaking: Added as a new function (regulate_ph_ec_v2), does not modify the existing regulate_ph_ec.py
• All options configurable: No hardcoded values — setpoints, limits, pump IDs, Telegram credentials all via custom_options
• Graceful degradation: Telegram is optional (just leave token empty), water level sensor is optional, EC pumps C/D are optional
• Daily limits prevent runaway dosing: If sensors malfunction and report permanently low values, the daily ml cap prevents overdosing
• In-band halving: When pH/EC is within the regulation band but on the wrong side of setpoint, dose is halved for smooth convergence instead of aggressive correction

Testing

Tested on a production Raspberry Pi 4B running Mycodo v8.16.2 with:

• DFRobot pH + EC sensors via ADS1115
• 8× peristaltic dosing pumps (HW-283 relay module)
• YF-S401 flow sensor
• XKC-Y25-NPN water level sensors
• Running 24/7 for 4 weeks managing a single-plant hydroponic NFT system

Target

This PR is on the fork for review. Intended for upstream submission to kizniche/Mycodo once validated.

Checklist

• No hardcoded UUIDs or installation-specific values
• All strings in English
• GPL-3.0 license header
• Uses lazy_gettext for translatable option labels
• Valid Python syntax
• Follows Mycodo custom function conventions
• Unit tests (to be added before upstream PR)