fix: optimize SQLite connection pooling for single-writer architecture

Remove misleading max_connections config option and properly configure
SQLite connection pooling in the storage layer.

Changes:
- Set MaxOpenConns(1) for optimal SQLite performance
- Set MaxIdleConns(1) to keep connection alive
- Set ConnMaxLifetime(0) to never close connection
- Remove max_connections and max_lifetime from DatabaseConfig
- Update docs to clarify SQLite's single-writer architecture

Rationale:
SQLite is an embedded database with a single-writer lock. Multiple
connections cause lock contention and reduce performance. WAL mode
allows concurrent reads from the same connection, making connection
pooling unnecessary and counterproductive.

This change makes the configuration clearer and ensures optimal
SQLite performance by using a single long-lived connection.

1 files changed, 2 insertions, 7 deletions

diff --git a/internal/config/README.md b/internal/config/README.md
index 87d6fa1..79e1b89 100644
--- a/internal/config/README.md
+++ b/internal/config/README.md
@@ -75,11 +75,8 @@ database:
   # Path to SQLite database file
   path: "relay.db"
 
-  # Maximum number of open connections
-  max_connections: 10
-
-  # Connection max lifetime
-  max_lifetime: "1h"
+  # Note: Connection pooling is automatically configured for SQLite.
+  # SQLite uses a single connection for optimal performance.
 
 # Authentication configuration
 auth:
@@ -264,8 +261,6 @@ Server:
 
 Database:
   Path: "relay.db"
-  MaxConnections: 10
-  MaxLifetime: 1h
 
 Auth:
   Enabled: false