Persist Wordle guesses, fix hardcoded rendering, announce expired puzzles

- Add wordle_guesses table to persist individual guesses to DB
- Reload guesses during rehydration so they survive bot restarts
- Clear stale guesses when puzzle is replaced (skip+new)
- Fix all hardcoded /6 and 🟩🟩🟩🟩🟩 in rendering to use puzzle.MaxGuesses
  and puzzle.WordLength
- Announce unsolved puzzles at midnight rollover instead of silently replacing
- Mark expired puzzles as failed and update stats on rollover

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/db/db.go

@@ -822,6 +822,17 @@ CREATE TABLE IF NOT EXISTS wordle_puzzles (
 	PRIMARY KEY (puzzle_id, room_id)
 );
 
+CREATE TABLE IF NOT EXISTS wordle_guesses (
+	puzzle_id    TEXT NOT NULL,
+	room_id      TEXT NOT NULL,
+	guess_num    INTEGER NOT NULL,
+	word         TEXT NOT NULL,
+	player_id    TEXT NOT NULL,
+	player_name  TEXT NOT NULL,
+	guessed_at   DATETIME NOT NULL,
+	PRIMARY KEY (puzzle_id, room_id, guess_num)
+);
+
 -- Space groups (rooms with overlapping membership)
 CREATE TABLE IF NOT EXISTS space_groups (
 	room_id    TEXT PRIMARY KEY,