Add database cleanup feature to empty all sensor tables

Added a "Danger Zone" section on the database page that allows users to empty all sensor data tables while preserving configuration and timestamp tables. The feature includes:

- New Python script (sqlite/empty_sensor_tables.py) to safely empty sensor tables
- Backend endpoint in launcher.php (empty_sensor_tables)
- Frontend UI with red warning card and confirmation dialog
- Detailed feedback showing deleted record counts per table
- i18n support for French and English

Tables emptied: data_NPM, data_NPM_5channels, data_BME280, data_envea, data_WIND, data_MPPT, data_NOISE, modem_status
Tables preserved: timestamp_table, config_table, envea_sondes_table, config_scripts_table

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

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

html/database.html

@@ -108,6 +108,17 @@
             </div>
           </div>
 
+          <div class="col-sm-5">
+            <div class="card text-white bg-danger">
+              <div class="card-body">
+                <h5 class="card-title" data-i18n="database.dangerZone">Zone dangereuse</h5>
+                <p class="card-text" data-i18n="database.dangerWarning">Attention: Cette action est irréversible!</p>
+                <button class="btn btn-dark" onclick="emptySensorTables()" data-i18n="database.emptyAllTables">Vider toutes les tables de capteurs</button>
+                <small class="d-block mt-2" data-i18n="database.emptyTablesNote">Note: Les tables de configuration et horodatage seront préservées.</small>
+              </div>
+            </div>
+          </div>
+
         <div>
 
         <div class="row mt-2">
@@ -441,6 +452,74 @@ function downloadCSV(response, table) {
     document.body.removeChild(a);
 }
 
+// Function to empty all sensor tables
+function emptySensorTables() {
+    // Show confirmation dialog
+    const confirmed = confirm(
+        "WARNING: This will permanently delete ALL sensor data from the database!\n\n" +
+        "The following tables will be emptied:\n" +
+        "- data_NPM\n" +
+        "- data_NPM_5channels\n" +
+        "- data_BME280\n" +
+        "- data_envea\n" +
+        "- data_WIND\n" +
+        "- data_MPPT\n" +
+        "- data_NOISE\n\n" +
+        "Configuration and timestamp tables will be preserved.\n\n" +
+        "Are you absolutely sure you want to continue?"
+    );
+
+    if (!confirmed) {
+        console.log("Empty sensor tables operation cancelled by user");
+        return;
+    }
+
+    // Show loading message
+    const tableDataDiv = document.getElementById("table_data");
+    tableDataDiv.innerHTML = '<div class="alert alert-info">Emptying sensor tables... Please wait...</div>';
+
+    // Make AJAX request to empty tables
+    $.ajax({
+        url: 'launcher.php?type=empty_sensor_tables',
+        dataType: 'json',
+        method: 'GET',
+        success: function(response) {
+            console.log("Empty sensor tables response:", response);
+
+            if (response.success) {
+                // Show success message
+                let message = '<div class="alert alert-success">';
+                message += '<h5>Success!</h5>';
+                message += '<p>' + response.message + '</p>';
+
+                if (response.tables_processed && response.tables_processed.length > 0) {
+                    message += '<p><strong>Tables emptied:</strong></p><ul>';
+                    response.tables_processed.forEach(table => {
+                        message += `<li>${table.name}: ${table.deleted} records deleted</li>`;
+                    });
+                    message += '</ul>';
+                }
+
+                message += '</div>';
+                tableDataDiv.innerHTML = message;
+            } else {
+                // Show error message
+                tableDataDiv.innerHTML = `<div class="alert alert-danger">
+                    <h5>Error!</h5>
+                    <p>${response.message || response.error || 'Unknown error occurred'}</p>
+                </div>`;
+            }
+        },
+        error: function(xhr, status, error) {
+            console.error('AJAX request failed:', status, error);
+            tableDataDiv.innerHTML = `<div class="alert alert-danger">
+                <h5>Error!</h5>
+                <p>Failed to empty sensor tables: ${error}</p>
+            </div>`;
+        }
+    });
+}
+
 
 </script>