Merge branch 'main' into feature/tier2-channel-modes

Implement the second tier of IRC channel features:

1. Ban system (+b): Add/remove/list bans with wildcard matching.
   Bans prevent both joining and sending messages.
   Schema: channel_bans table with mask, set_by, created_at.

2. Invite-only (+i): Channel mode requiring invitation to join.
   INVITE command for operators. Invites stored in DB and
   cleared after successful JOIN.

3. Secret (+s): Hides channel from LIST for non-members and
   from WHOIS channel lists when querier is not in same channel.

4. Channel key (+k): Password-protected channels. Key required
   on JOIN, set/cleared by operators.

5. User limit (+l): Maximum member count enforcement. Rejects
   JOIN when channel is at capacity.

Updated ISUPPORT CHANMODES to b,k,Hl,imnst.
Updated RPL_MYINFO available modes to ikmnostl.
Comprehensive tests for all features at both DB and handler levels.
README updated with full documentation of all new modes.

closes #86

internal/db/db.go

@@ -135,21 +135,13 @@ type migration struct {
 func (database *Database) runMigrations(
 	ctx context.Context,
 ) error {
-	bootstrap, err := SchemaFiles.ReadFile(
-		"schema/000.sql",
-	)
+	_, err := database.conn.ExecContext(ctx,
+		`CREATE TABLE IF NOT EXISTS schema_migrations (
+		 version INTEGER PRIMARY KEY,
+		 applied_at DATETIME DEFAULT CURRENT_TIMESTAMP)`)
 	if err != nil {
 		return fmt.Errorf(
-			"read bootstrap migration: %w", err,
-		)
-	}
-
-	_, err = database.conn.ExecContext(
-		ctx, string(bootstrap),
-	)
-	if err != nil {
-		return fmt.Errorf(
-			"execute bootstrap migration: %w", err,
+			"create schema_migrations: %w", err,
 		)
 	}
 
@@ -278,11 +270,6 @@ func (database *Database) loadMigrations() (
 			continue
 		}
 
-		// Skip bootstrap migration; it is executed separately.
-		if version == 0 {
-			continue
-		}
-
 		content, readErr := SchemaFiles.ReadFile(
 			"schema/" + entry.Name(),
 		)

internal/db/schema/000.sql

@@ -1,6 +0,0 @@
--- Bootstrap: create the schema_migrations table itself.
-CREATE TABLE IF NOT EXISTS schema_migrations (
-    version INTEGER PRIMARY KEY,
-    applied_at DATETIME DEFAULT CURRENT_TIMESTAMP
-);
-INSERT OR IGNORE INTO schema_migrations (version) VALUES (0);