Complete rewrite: SnapRAID SMART logger with BackBlaze algorithm

Fetches SMART data from Scrutiny's InfluxDB and calculates failure
probabilities using the exact BackBlaze tables from SnapRAID source.

Key features:
- Calculates both v12 (with attr 193) and v13 (without attr 193) algorithms
- v12 matches SnapRAID pre-v13.0 (includes Load Cycle Count)
- v13 matches modern SnapRAID v13.0+ (excludes Load Cycle Count)
- Stores both values for trending and comparison
- Correctly applies bit masks (16-bit for 187/188, 32-bit for others)
- Annualizes monthly rates and applies Poisson distribution
- Logs to PostgreSQL with device metadata

Solved the mystery: SnapRAID v12 uses attribute 193 which was removed
in v13.0. Load cycle count has massive impact on failure predictions
for some drives (80% vs 4% difference).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

schema_migration_add_v13.sql

@@ -0,0 +1,72 @@
+-- Migration: Add v13.0 failure probability column
+-- Adds a second failure probability column for the modern algorithm (without attr 193)
+
+-- Add new column for v13.0+ algorithm (without attribute 193)
+ALTER TABLE smart_metrics
+ADD COLUMN IF NOT EXISTS failure_probability_v13_pct DECIMAL(5, 2);
+
+-- Rename existing column to clarify it includes attribute 193 (pre-v13.0)
+ALTER TABLE smart_metrics
+RENAME COLUMN failure_probability_pct TO failure_probability_v12_pct;
+
+-- Update views to include both columns
+DROP VIEW IF EXISTS smart_latest CASCADE;
+CREATE VIEW smart_latest AS
+SELECT
+    m.id,
+    m.timestamp,
+    m.device_wwn,
+    d.device_path,
+    d.serial_number,
+    d.model,
+    d.manufacturer,
+    d.capacity_bytes,
+    d.size_tb,
+    d.disk_role,
+    m.temperature_celsius,
+    m.power_on_days,
+    m.error_count,
+    m.failure_probability_v12_pct,  -- With attr 193 (matches your current SnapRAID)
+    m.failure_probability_v13_pct,  -- Without attr 193 (modern SnapRAID v13.0+)
+    m.smart_attributes
+FROM smart_metrics m
+INNER JOIN devices d ON m.device_wwn = d.device_wwn
+WHERE m.timestamp = (
+    SELECT MAX(m2.timestamp)
+    FROM smart_metrics m2
+    WHERE m2.device_wwn = m.device_wwn
+);
+
+DROP VIEW IF EXISTS smart_high_risk;
+CREATE VIEW smart_high_risk AS
+SELECT *
+FROM smart_latest
+WHERE failure_probability_v12_pct > 50  -- Using v12 since that matches your SnapRAID
+ORDER BY failure_probability_v12_pct DESC;
+
+DROP VIEW IF EXISTS smart_summary;
+CREATE VIEW smart_summary AS
+SELECT
+    device_path,
+    serial_number,
+    temperature_celsius,
+    power_on_days,
+    error_count,
+    failure_probability_v12_pct,  -- With attr 193
+    failure_probability_v13_pct,  -- Without attr 193
+    size_tb,
+    disk_role
+FROM smart_latest
+ORDER BY
+    CASE disk_role
+        WHEN 'parity' THEN 1
+        WHEN '2-parity' THEN 2
+        ELSE 3
+    END,
+    device_path;
+
+COMMENT ON COLUMN smart_metrics.failure_probability_v12_pct IS
+    'Failure probability using SnapRAID <v13.0 algorithm (includes attribute 193 Load Cycle Count)';
+
+COMMENT ON COLUMN smart_metrics.failure_probability_v13_pct IS
+    'Failure probability using SnapRAID v13.0+ algorithm (excludes attribute 193)';