feat: implement Tier 1 channel modes (+o/+v/+m/+t), KICK, NOTICE

Implement core IRC channel functionality:

1. Channel member flags: is_operator and is_voiced columns in
   channel_members table (proper boolean columns per sneak's
   instruction, not text string modes).

2. MODE +o/+v/-o/-v: Grant/revoke operator and voice status.
   Permission-checked (only +o can grant). NAMES replies show
   @nick for operators and +nick for voiced users.

3. MODE +m (moderated): Only +o and +v users can send PRIVMSG
   or NOTICE to moderated channels. Others get ERR_CANNOTSENDTOCHAN.

4. MODE +t (topic lock): Only +o can change topic when active.
   Default ON for new channels (standard IRC behavior). Others
   get ERR_CHANOPRIVSNEEDED.

5. KICK command: Operator-only, removes user from channel,
   broadcasts to all members including kicked user.

6. NOTICE differentiation: No RPL_AWAY auto-reply, skips hashcash
   validation on +H channels per RFC 2812.

Additional improvements:
- Channel creator auto-gets +o on first JOIN
- ISUPPORT now advertises PREFIX=(ov)@+ and CHANMODES=,,H,mnst
- MODE query shows accurate +nt/+m/+H mode string
- Fixed pre-existing unparam lint issue in fanOutSilent

Includes 22 new tests covering all requirements.

closes #85

internal/db/schema/001_initial.sql

@@ -40,6 +40,8 @@ CREATE TABLE IF NOT EXISTS channels (
     topic_set_by TEXT NOT NULL DEFAULT '',
     topic_set_at DATETIME,
     hashcash_bits INTEGER NOT NULL DEFAULT 0,
+    is_moderated INTEGER NOT NULL DEFAULT 0,
+    is_topic_locked INTEGER NOT NULL DEFAULT 1,
     created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
     updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
 );
@@ -49,6 +51,8 @@ CREATE TABLE IF NOT EXISTS channel_members (
     id INTEGER PRIMARY KEY AUTOINCREMENT,
     channel_id INTEGER NOT NULL REFERENCES channels(id) ON DELETE CASCADE,
     session_id INTEGER NOT NULL REFERENCES sessions(id) ON DELETE CASCADE,
+    is_operator INTEGER NOT NULL DEFAULT 0,
+    is_voiced INTEGER NOT NULL DEFAULT 0,
     joined_at DATETIME DEFAULT CURRENT_TIMESTAMP,
     UNIQUE(channel_id, session_id)
 );