refactor(handlers): migrate remaining backend handlers to clock.Now() and transaction patterns

Apply clock.Now() migration, transaction wrapping, and minor refactors across admin, scheduling, today, user, auth handler, notifications, webhooks, services, portfolio, ratelimit, testutils, and main.go.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/mw/ratelimit.go

@@ -4,7 +4,9 @@
 package mw
 
 import (
+	"crussell/clock"
 	"fmt"
+	"log"
 	"net/http"
 	"sync"
 	"net"
@@ -28,8 +30,15 @@ func NewRateLimiter(limit int, window time.Duration) *RateLimiter {
 	// Cleanup old entries periodically
 	go func() {
 		for {
-			time.Sleep(window)
-			rl.cleanup()
+			func() {
+				defer func() {
+					if r := recover(); r != nil {
+						log.Printf("Panic recovered in rate limiter cleanup: %v", r)
+					}
+				}()
+				time.Sleep(window)
+				rl.cleanup()
+			}()
 		}
 	}()
 	return rl
@@ -38,7 +47,7 @@ func NewRateLimiter(limit int, window time.Duration) *RateLimiter {
 func (rl *RateLimiter) cleanup() {
 	rl.mu.Lock()
 	defer rl.mu.Unlock()
-	now := time.Now()
+	now := clock.Now()
 	for key, times := range rl.requests {
 		var valid []time.Time
 		for _, t := range times {
@@ -57,7 +66,7 @@ func (rl *RateLimiter) cleanup() {
 func (rl *RateLimiter) Allow(key string) bool {
 	rl.mu.Lock()
 	defer rl.mu.Unlock()
-	now := time.Now()
+	now := clock.Now()
 	windowStart := now.Add(-rl.window)
 
 	var valid []time.Time
@@ -94,8 +103,15 @@ func NewProgressiveRateLimiter() *ProgressiveRateLimiter {
 	}
 	go func() {
 		for {
-			time.Sleep(30 * time.Second)
-			prl.cleanup()
+			func() {
+				defer func() {
+					if r := recover(); r != nil {
+						log.Printf("Panic recovered in progressive rate limiter cleanup: %v", r)
+					}
+				}()
+				time.Sleep(30 * time.Second)
+				prl.cleanup()
+			}()
 		}
 	}()
 	return prl
@@ -104,7 +120,7 @@ func NewProgressiveRateLimiter() *ProgressiveRateLimiter {
 func (prl *ProgressiveRateLimiter) cleanup() {
 	prl.mu.Lock()
 	defer prl.mu.Unlock()
-	cutoff := time.Now().Add(-60 * time.Second)
+	cutoff := clock.Now().Add(-60 * time.Second)
 	for ip, state := range prl.requests {
 		var valid []time.Time
 		for _, t := range state.timestamps {
@@ -130,7 +146,7 @@ func (prl *ProgressiveRateLimiter) Check(ip string) (delayMs int) {
 	prl.mu.Lock()
 	defer prl.mu.Unlock()
 
-	now := time.Now()
+	now := clock.Now()
 	state, exists := prl.requests[ip]
 	if !exists {
 		prl.requests[ip] = &ipProgressiveState{

backend/mw/ratelimit_test.go

@@ -7,6 +7,8 @@ import (
 	"sync"
 	"testing"
 	"time"
+
+	"crussell/clock"
 )
 
 // TestProgressiveRateLimiter_SingleRequest verifies no delay for first request.
@@ -60,12 +62,12 @@ func TestProgressiveRateLimiter_SustainedAllowsNormal(t *testing.T) {
 		state, exists := prl.requests[ip]
 		if !exists {
 			prl.requests[ip] = &ipProgressiveState{
-				timestamps: []time.Time{time.Now().Add(-time.Duration(60-i*2) * time.Second)},
+				timestamps: []time.Time{clock.Now().Add(-time.Duration(60-i*2) * time.Second)},
 			}
 			prl.mu.Unlock()
 			continue
 		}
-		state.timestamps = append(state.timestamps, time.Now().Add(-time.Duration(60-i*2)*time.Second))
+		state.timestamps = append(state.timestamps, clock.Now().Add(-time.Duration(60-i*2)*time.Second))
 		prl.mu.Unlock()
 	}
 
@@ -81,7 +83,7 @@ func TestProgressiveRateLimiter_ExcessSustainedDelays(t *testing.T) {
 	prl := NewProgressiveRateLimiter()
 	ip := "192.168.1.3"
 
-	now := time.Now()
+	now := clock.Now()
 	prl.mu.Lock()
 	state := &ipProgressiveState{timestamps: make([]time.Time, 130)}
 	for i := 0; i < 130; i++ {
@@ -118,7 +120,7 @@ func TestProgressiveRateLimiter_CleanupRemovesStaleEntries(t *testing.T) {
 
 	prl.mu.Lock()
 	prl.requests["stale-ip"] = &ipProgressiveState{
-		timestamps: []time.Time{time.Now().Add(-120 * time.Second)},
+		timestamps: []time.Time{clock.Now().Add(-120 * time.Second)},
 	}
 	prl.mu.Unlock()