Add data retention configuration and cleanup functionality

- Introduced a new `[Data_Retention]` section in `config.ini.example` to manage retention periods for various database tables, including packet stream, daily stats, and observed paths.
- Updated `mkdocs.yml` and `configuration.md` to include documentation for the new data retention settings.
- Implemented data retention cleanup methods in `mesh_graph.py`, `repeater_manager.py`, and `scheduler.py` to enforce retention policies automatically.
- Enhanced the web viewer's data cleanup logic to utilize the new retention settings, ensuring efficient database management.

docs/configuration.md

@@ -56,6 +56,10 @@ Examples of sections that configure specific commands or features:
 
 Full reference: see `config.ini.example` in the repository for every section and option, with inline comments.
 
+## Data retention
+
+Database tables (packet stream, stats, repeater data, mesh graph) are pruned automatically. Retention periods and defaults are described in **[Data retention](data-retention.md)**. The bot’s scheduler runs cleanup daily even when the standalone web viewer is not running.
+
 ## Path Command configuration
 
 The Path command has many options (presets, proximity, graph validation, etc.). All are documented in:

docs/data-retention.md

@@ -0,0 +1,45 @@
+# Data retention
+
+The bot stores data in a SQLite database for the web viewer, stats, repeater management, and path routing. To limit database size, **data retention** controls how long rows are kept. Cleanup runs **daily** from the bot’s scheduler, so retention is enforced even when the standalone web viewer is not running.
+
+## Configuration
+
+All retention options live in the **`[Data_Retention]`** section of `config.ini`. Example (see `config.ini.example` for full comments):
+
+```ini
+[Data_Retention]
+packet_stream_retention_days = 3
+daily_stats_retention_days = 90
+observed_paths_retention_days = 90
+purging_log_retention_days = 90
+mesh_connections_retention_days = 7
+```
+
+Stats tables (message_stats, command_stats, path_stats) use **`[Stats_Command]`** `data_retention_days` (default 7); the scheduler runs that cleanup daily as well.
+
+## Tables and defaults
+
+| Table / data | Purpose | Default retention |
+|--------------|---------|--------------------|
+| **packet_stream** | Real-time packets, commands, routing in the web viewer; transmission_tracker repeat counts | 3 days |
+| **daily_stats** | Daily repeater/advert stats | 90 days |
+| **unique_advert_packets** | Unique packet hashes for advert stats | 90 days (same as daily_stats) |
+| **observed_paths** | Path strings from adverts and messages | 90 days |
+| **purging_log** | Audit trail for repeater purges | 90 days |
+| **mesh_connections** | Path graph edges (in-memory + DB); should be ≥ Path_Command `graph_edge_expiration_days` | 7 days |
+| **message_stats, command_stats, path_stats** | Stats command data | 7 days (`[Stats_Command]` `data_retention_days`) |
+| **geocoding_cache, generic_cache** | Expired entries removed by scheduler | By expiry time |
+
+Shorter retention (e.g. 2–3 days for `packet_stream`) is enough for the web viewer and transmission_tracker; longer retention is only needed if you want more history.
+
+## How cleanup runs
+
+1. The **scheduler** (in the main bot process) runs a single data-retention task once every 24 hours.
+2. That task:
+   - Cleans **packet_stream** (via web viewer integration when enabled).
+   - Cleans **purging_log**, **daily_stats**, **unique_advert_packets**, and **observed_paths** (repeater manager).
+   - Cleans **message_stats**, **command_stats**, **path_stats** (stats command’s `cleanup_old_stats`).
+   - Removes expired rows from **geocoding_cache** and **generic_cache** (DB manager).
+   - Deletes old rows from **mesh_connections** (mesh graph).
+
+So as long as the bot is running, the database is pruned on a schedule regardless of whether you run the standalone web viewer or the stats command.