docs: document statistics optimization and fix entity ID examples

Add coverage for the state_class/statistics table optimization across
both user and developer documentation.

docs/user/docs/configuration.md:
- Add 'Price Sensor Statistics' section explaining that only 3 sensors
  write to the HA statistics database (current_interval_price,
  current_interval_price_base, average_price_today)
- Fix incorrect entity ID examples: remove non-existent _override suffix
  from recorder exclude globs, Developer Tools example, and seasonal
  automation example (actual IDs: number.*_best_price_flexibility etc.)

docs/developer/docs/recorder-optimization.md:
- Add 'Long-Term Statistics Optimization (state_class)' section covering
  the statistics/statistics_short_term table dimension, which is distinct
  from _unrecorded_attributes (state_attributes table)
- Documents the MONETARY device_class constraint (MEASUREMENT blocked by
  hassfest, only TOTAL or None valid), the 3 sensors keeping TOTAL with
  rationale, the 23 sensors set to None, and ~88% write reduction
- Includes comparison table: _unrecorded_attributes vs state_class

Impact: Users now understand the built-in statistics optimization and
have correct recorder exclude examples. Developers understand both
optimization layers and their interaction.

docs/developer/docs/recorder-optimization.md

@@ -283,6 +283,73 @@ LIMIT 5;
 - ✅ Attributes still available via `entity.attributes` in templates/automations
 - ✅ Only prevents **storage** in Recorder, not runtime availability
 
+## Long-Term Statistics Optimization (`state_class`)
+
+**This is a second, independent mechanism** that controls writes to the HA `statistics` and `statistics_short_term` tables — distinct from `_unrecorded_attributes`, which only affects the `state_attributes` table.
+
+### Why This Matters
+
+- The `state_attributes` table (controlled by `_unrecorded_attributes`) is **auto-purged** after ~10 days
+- The `statistics`/`statistics_short_term` tables (controlled by `state_class`) are **never auto-purged** — they grow unbounded
+
+This makes `state_class=TOTAL` on many sensors the primary cause of long-term database bloat for users with long-running installations.
+
+### HA Constraint: MONETARY Device Class
+
+For sensors with `device_class=SensorDeviceClass.MONETARY`, only two `state_class` values are valid:
+
+| `state_class` | Statistics written | Frontend effect |
+|---|---|---|
+| `TOTAL` | ✅ Yes — unbounded growth | Statistics line-chart on entity detail page |
+| `None` | ❌ No | States timeline only (History panel, "Show More") |
+| `MEASUREMENT` | ❌ Blocked by hassfest | — |
+
+`MEASUREMENT` causes a hassfest validation error for MONETARY sensors, leaving only `TOTAL` or `None`.
+
+### Implementation Decision
+
+Only 3 of 26 MONETARY sensors keep `state_class=TOTAL` — those where long-term history is genuinely useful:
+
+| Sensor | Reason |
+|---|---|
+| `current_interval_price` | Long-term price trend (weeks/months) |
+| `current_interval_price_base` | Required for Energy Dashboard |
+| `average_price_today` | Seasonal daily average tracking |
+
+All other 23 MONETARY sensors use `state_class=None`:
+- Forecast/future sensors (`next_avg_*h`)
+- Daily snapshots (`lowest/highest_price_today/tomorrow`)
+- Rolling windows (`trailing/leading_24h_*`)
+- Next/previous interval sensors
+
+**Effect of `state_class=None`:**
+- ✅ Short-term state history (States timeline, ~10 days) still works normally
+- ✅ Templates, automations, and attributes are unaffected
+- ❌ Statistics line-chart removed from entity detail page for these sensors
+- ❌ No writes to `statistics`/`statistics_short_term` tables
+
+### Expected Impact
+
+Going from 26 → 3 sensors writing to the statistics tables:
+- **~88% reduction** in statistics table writes
+- Prevents the primary cause of long-term database bloat
+- Existing statistics data is retained (only new writes stop)
+
+### Relationship to `_unrecorded_attributes`
+
+These are two independent mechanisms targeting different tables:
+
+| Mechanism | Table affected | Purged? | Controls |
+|---|---|---|---|
+| `_unrecorded_attributes` | `state_attributes` | ✅ ~10 days | Which attributes are stored per state write |
+| `state_class=None` | `statistics`, `statistics_short_term` | ❌ Never | Whether long-term statistics are written at all |
+
+Both optimizations work together. `_unrecorded_attributes` reduces the size of each state write; `state_class=None` eliminates an entire category of unbounded writes.
+
+### Implementation File
+
+- **`custom_components/tibber_prices/sensor/definitions.py`** — `state_class` set per-sensor in `SensorEntityDescription`
+
 ## References
 
 - [HA Developer Docs - Excluding State Attributes](https://developers.home-assistant.io/docs/core/entity/#excluding-state-attributes-from-recorder-history)

docs/user/docs/configuration.md

@@ -129,7 +129,7 @@ Each configuration entity includes a detailed description attribute explaining w
 **Note:** For **Number entities**, Home Assistant displays a history graph by default, which hides the attributes panel. To view the `description` attribute:
 
 1. Go to **Developer Tools → States**
-2. Search for the entity (e.g., `number.<home_name>_best_price_flexibility_override`)
+2. Search for the entity (e.g., `number.<home_name>_best_price_flexibility`)
 3. Expand the attributes section to see the full description
 
 **Switch entities** display their attributes normally in the entity details view.
@@ -148,7 +148,7 @@ automation:
     action:
       - service: number.set_value
         target:
-          entity_id: number.<home_name>_best_price_flexibility_override
+          entity_id: number.<home_name>_best_price_flexibility
         data:
           value: 10  # Stricter than default 15%
 ```
@@ -169,13 +169,25 @@ recorder:
   exclude:
     entity_globs:
       # Exclude all Tibber Prices configuration entities
-      - number.*_best_price_*_override
+      - number.*_best_price_*
-      - number.*_peak_price_*_override
+      - number.*_peak_price_*
-      - switch.*_best_price_*_override
+      - switch.*_best_price_*
-      - switch.*_peak_price_*_override
+      - switch.*_peak_price_*
 ```
 
 This is especially useful if:
 - You rarely change these settings
 - You want the smallest possible database footprint
 - You don't need to see the history graph for these entities
+
+#### Price Sensor Statistics
+
+The integration also minimizes long-term statistics growth for price sensors. Only 3 sensors write to the HA statistics database (which is never auto-purged):
+
+- **Current Electricity Price** — Long-term price trend over weeks/months
+- **Current Electricity Price (Energy Dashboard)** — Required for Energy Dashboard integration
+- **Today's Average Price** — Seasonal price comparison
+
+All other price sensors (forecasts, rolling averages, daily min/max, future averages) have long-term statistics disabled. Their **state history** (the step chart in the History panel) still works normally for ~10 days — only the smooth statistics line-chart on the entity detail page is absent for these sensors.
+
+No configuration changes are needed — this optimization is built into the integration.