feat: implement IRC numerics batch 2 — connection registration, channel ops, user queries

Add comprehensive IRC numeric reply support:

Connection registration (001-005):
- 002 RPL_YOURHOST, 003 RPL_CREATED, 004 RPL_MYINFO, 005 RPL_ISUPPORT
- All sent automatically during session creation after RPL_WELCOME

Server statistics (251-255):
- RPL_LUSERCLIENT, RPL_LUSEROP, RPL_LUSERCHANNELS, RPL_LUSERME
- Sent during connection registration and via LUSERS command

Channel operations:
- MODE command: query channel modes (324 RPL_CHANNELMODEIS, 329 RPL_CREATIONTIME)
- MODE command: query user modes (221 RPL_UMODEIS)
- NAMES command: query channel member list (353/366)
- LIST command: list all channels (322 RPL_LIST, 323 end of list)

User queries:
- WHOIS command: 311/312/318/319 numerics
- WHO command: 352 RPL_WHOREPLY, 315 RPL_ENDOFWHO

Database additions:
- GetChannelCount, ListAllChannelsWithCounts
- GetChannelCreatedAt, GetSessionCreatedAt

Also adds StartTime to Globals for RPL_CREATED and updates README
with comprehensive documentation of all new commands and numerics.

closes #52

internal/globals/globals.go

@@ -2,6 +2,8 @@
 package globals
 
 import (
+	"time"
+
 	"go.uber.org/fx"
 )
 
@@ -15,16 +17,18 @@ var (
 
 // Globals holds application-wide metadata.
 type Globals struct {
-	Appname string
-	Version string
+	Appname   string
+	Version   string
+	StartTime time.Time
 }
 
 // New creates a new Globals instance from the global state.
 func New(_ fx.Lifecycle) (*Globals, error) {
-	n := &Globals{
-		Appname: Appname,
-		Version: Version,
+	result := &Globals{
+		Appname:   Appname,
+		Version:   Version,
+		StartTime: time.Now(),
 	}
 
-	return n, nil
+	return result, nil
 }