Rewrite from TypeScript to Go

Complete rewrite of the Freebee Matrix bot as GogoBee using mautrix-go.

- E2EE with goolm (pure Go, no CGo/libolm) and cross-signing bootstrap
- 35+ plugins with dependency injection and ordered registration
- SQLite storage via modernc.org/sqlite (no CGo)
- Scheduler via robfig/cron for WOTD, holidays, birthdays, releases, etc.
- Optional LLM integration (Ollama) for sentiment, profanity, roasts, vibes
- Threaded trivia, three-tier profanity tracking, WOTD usage verification
- Multi-country holiday support with deduplication
- Quadratic XP curve, configurable bot display name, encrypted DMs

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

internal/plugin/ratelimits.go

@@ -0,0 +1,95 @@
+package plugin
+
+import (
+	"log/slog"
+	"time"
+
+	"gogobee/internal/db"
+
+	"maunium.net/go/mautrix"
+	"maunium.net/go/mautrix/id"
+)
+
+// RateLimitsPlugin provides rate-limiting utilities for other plugins.
+type RateLimitsPlugin struct {
+	Base
+}
+
+// NewRateLimitsPlugin creates a new rate limits plugin.
+func NewRateLimitsPlugin(client *mautrix.Client) *RateLimitsPlugin {
+	return &RateLimitsPlugin{
+		Base: NewBase(client),
+	}
+}
+
+func (p *RateLimitsPlugin) Name() string { return "ratelimits" }
+
+func (p *RateLimitsPlugin) Commands() []CommandDef { return nil }
+
+func (p *RateLimitsPlugin) Init() error { return nil }
+
+func (p *RateLimitsPlugin) OnMessage(_ MessageContext) error { return nil }
+
+func (p *RateLimitsPlugin) OnReaction(_ ReactionContext) error { return nil }
+
+// CheckLimit returns true if the user is under the rate limit for the given action.
+// Admin users always bypass rate limits.
+func (p *RateLimitsPlugin) CheckLimit(userID id.UserID, action string, maxPerDay int) bool {
+	if p.IsAdmin(userID) {
+		return true
+	}
+
+	d := db.Get()
+	today := time.Now().UTC().Format("2006-01-02")
+
+	// Atomic check-and-increment: only increment if under limit
+	// This avoids the TOCTOU race between SELECT and UPDATE
+	_, err := d.Exec(
+		`INSERT INTO rate_limits (user_id, action, date, count) VALUES (?, ?, ?, 1)
+		 ON CONFLICT(user_id, action, date) DO UPDATE SET count = count + 1
+		 WHERE count < ?`,
+		string(userID), action, today, maxPerDay,
+	)
+	if err != nil {
+		slog.Error("ratelimits: increment", "err", err)
+		return true // Fail open on error
+	}
+
+	// Check current count to determine if we're over limit
+	var count int
+	err = d.QueryRow(
+		`SELECT count FROM rate_limits WHERE user_id = ? AND action = ? AND date = ?`,
+		string(userID), action, today,
+	).Scan(&count)
+	if err != nil {
+		return true // Fail open
+	}
+
+	return count <= maxPerDay
+}
+
+// Remaining returns how many uses remain for the given action today.
+// Admin users get maxPerDay (effectively unlimited).
+func (p *RateLimitsPlugin) Remaining(userID id.UserID, action string, maxPerDay int) int {
+	if p.IsAdmin(userID) {
+		return maxPerDay
+	}
+
+	d := db.Get()
+	today := time.Now().UTC().Format("2006-01-02")
+
+	var count int
+	err := d.QueryRow(
+		`SELECT count FROM rate_limits WHERE user_id = ? AND action = ? AND date = ?`,
+		string(userID), action, today,
+	).Scan(&count)
+	if err != nil {
+		count = 0
+	}
+
+	remaining := maxPerDay - count
+	if remaining < 0 {
+		return 0
+	}
+	return remaining
+}