feat: add UserResource with is_admin toggle and delete

User management resource with editable is_admin field, postcode support,
admin filter, and inline delete action. Includes list and edit pages.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/rules/scoring.md

@@ -6,15 +6,20 @@ Produces a "fill up now or wait?" recommendation per user based on their local
 station history. Output is one of: `fill_up`, `wait`, `no_signal`.
 Never guess — stay silent (no_signal) when signals conflict or data is insufficient.
 
-## The 4 signals (in priority order)
+## The 5 signals (in priority order)
 
 ### Signal 1 — Local price trend (HIGHEST WEIGHT)
 - Query `station_prices` for user's nearest 5 stations (within 5km of user lat/lng)
 - Use last 14 days of history for `e10` (or user's preferred fuel type)
-- Calculate 3-day rolling average vs 7-day rolling average
-- **Falling**: 3-day avg < 7-day avg by ≥ 0.5p → positive wait signal
-- **Rising**: 3-day avg > 7-day avg by ≥ 0.5p → fill_up signal
-- **Flat**: difference < 0.5p → neutral, no signal
+- **Use linear regression, not rolling averages:**
+    - Run least-squares regression on `(recorded_at, price_pence)` pairs
+    - Calculate slope (pence/day) and R² (goodness of fit, 0–1)
+    - Only use the regression result if R² ≥ 0.5 — below that, data is too noisy
+    - Use adaptive lookback: try 5 days first (best signal on sharp moves), fall back to 14 days if R² < 0.5
+- **Falling**: slope ≤ -0.3p/day AND R² ≥ 0.5 → wait signal, points scale with slope magnitude
+- **Rising**: slope ≥ +0.3p/day AND R² ≥ 0.5 → fill_up signal
+- **Flat / noisy**: |slope| < 0.3 OR R² < 0.5 → no signal from this source
+- Store slope, R², lookback_days, and data_points in signal output
 - Weight: 40 points max
 
 ### Signal 2 — Supermarket anchor effect (HIGH WEIGHT)
@@ -22,6 +27,7 @@ Never guess — stay silent (no_signal) when signals conflict or data is insuffi
 - Check if supermarket cut price in last 48 hours (> 1p drop)
 - Check if nearest non-supermarket stations have NOT yet followed
 - If supermarket cut AND independents haven't moved → strong wait signal
+- Also check the inverse: if supermarket RAISED and independents haven't → mild fill_up
 - Weight: 35 points max
 
 ### Signal 3 — Day-of-week pattern (MEDIUM WEIGHT — needs 8+ weeks data)
@@ -39,6 +45,16 @@ Never guess — stay silent (no_signal) when signals conflict or data is insuffi
 - Points awarded proportionally to confidence: `(confidence / 100) * 10`
 - Weight: 10 points max
 
+### Signal 5 — Price stickiness (CONFIDENCE MODIFIER)
+- Per station: calculate average hold duration (days between price changes) from history
+- Requires 30+ days of history to activate
+- Use as a confidence modifier, not a directional signal:
+    - avg hold < 2 days → reduce overall confidence by 5 points (volatile, hard to predict)
+    - avg hold 2–4 days → neutral, no adjustment
+    - avg hold > 5 days → increase overall confidence by 5 points (predictable, sticky)
+- Store avg_hold_days and data_points in signal output
+- Applied after all other signals are summed (±5 points)
+
 ## Confidence thresholds
 
 - Score 70–100: strong signal → fire recommendation + notification
@@ -51,29 +67,50 @@ Never guess — stay silent (no_signal) when signals conflict or data is insuffi
 
 ```php
 [
-    'recommendation' => 'wait',        // fill_up | wait | no_signal
-    'confidence'     => 78,            // 0-100
-    'signals'        => [
-        'trend'       => ['direction' => 'falling', 'points' => 32],
+    'recommendation'  => 'wait',
+    'confidence'      => 78,
+    'signals'         => [
+        'trend'       => [
+            'direction'     => 'falling',
+            'slope'         => -1.07,     // pence per day
+            'r_squared'     => 0.96,
+            'lookback_days' => 5,
+            'data_points'   => 5,
+            'points'        => 32,
+        ],
         'supermarket' => ['triggered' => true, 'points' => 35],
         'day_pattern' => ['triggered' => false, 'points' => 0],
         'brent'       => ['direction' => 'flat', 'points' => 0],
+        'stickiness'  => ['avg_hold_days' => 2.8, 'modifier' => 0],
     ],
-    'local_avg_pence' => 14380,        // 143.80p
-    'trend_delta'     => -2.3,         // pence change over 7 days
+    'local_avg_pence' => 14380,           // 143.80p
+    'trend_delta'     => -2.3,            // pence change over lookback period
 ]
 ```
 
 ## Human-readable reason strings
 
 Always generate a plain-English reason for the recommendation:
-- "Prices near you have been falling for 6 days. Tesco {station} cut 3p yesterday — independents usually follow within 48 hours."
-- "Prices are rising in your area — filling up today avoids paying more later."
+- "Prices near you have been falling at 1.1p/day for 5 days. Tesco {station} cut 3p yesterday — independents usually follow within 48 hours."
+- "Prices are rising sharply in your area (+7.5p expected this week) — filling up today avoids paying more later."
 - "No clear pattern this week — fill up at the cheapest station near you now."
 
 Reason strings are stored in `scoring_results.signals` JSON and shown in the UI and notifications.
 
+## Data quality — anomaly rejection
+
+The Fuel Finder API contains dirty data (live example: 1369.0p/litre in national index).
+Reject a price record before storing or scoring if:
+- `price_pence > 25000` (over 250p/litre — physically implausible for UK pump prices)
+- `price_pence < 10000` (under 100p/litre — almost certainly a decimal entry error)
+- Price changed by more than 20p in a single update from the same station
+  (flag for review, do not use in scoring)
+
+Log rejected records to an `anomalous_prices` table for monitoring.
+Never let a dirty data point skew the regression slope or collapse R².
+
 ## Accuracy self-tracking
 
 After 3 days, check if `wait` recommendation was correct (prices did fall further).
-Store outcome in `scoring_results` for future display: "This signal has been right X% of the time in your area."
+Store outcome in `scoring_results` for future display:
+"This signal has been right X% of the time in your area."