add IP to sessions, IP+hostname to clients

- Add ip column to sessions table (real client IP of session creator)
- Add ip and hostname columns to clients table (per-connection tracking)
- Update CreateSession, RegisterUser, LoginUser to store new fields
- Add GetClientHostInfo query method
- Update SessionHostInfo to include IP
- Extract executeCreateSession to fix funlen lint
- Add tests for session IP, client IP/hostname, login client tracking
- Update README with new field documentation

internal/db/schema/001_initial.sql

@@ -8,6 +8,7 @@ CREATE TABLE IF NOT EXISTS sessions (
     nick TEXT NOT NULL UNIQUE,
     username TEXT NOT NULL DEFAULT '',
     hostname TEXT NOT NULL DEFAULT '',
+    ip TEXT NOT NULL DEFAULT '',
     password_hash TEXT NOT NULL DEFAULT '',
     signing_key TEXT NOT NULL DEFAULT '',
     away_message TEXT NOT NULL DEFAULT '',
@@ -22,6 +23,8 @@ CREATE TABLE IF NOT EXISTS clients (
     uuid TEXT NOT NULL UNIQUE,
     session_id INTEGER NOT NULL REFERENCES sessions(id) ON DELETE CASCADE,
     token TEXT NOT NULL UNIQUE,
+    ip TEXT NOT NULL DEFAULT '',
+    hostname TEXT NOT NULL DEFAULT '',
     created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
     last_seen DATETIME DEFAULT CURRENT_TIMESTAMP
 );