deps: update vendor dependencies for S3-compatible storage

Updates AWS SDK and removes Blazer B2 dependency in favor of unified
S3-compatible approach. Includes configuration examples and documentation.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

vendor/github.com/aws/aws-sdk-go/internal/sdkrand/locked_source.go

@@ -0,0 +1,29 @@
+package sdkrand
+
+import (
+	"math/rand"
+	"sync"
+	"time"
+)
+
+// lockedSource is a thread-safe implementation of rand.Source
+type lockedSource struct {
+	lk  sync.Mutex
+	src rand.Source
+}
+
+func (r *lockedSource) Int63() (n int64) {
+	r.lk.Lock()
+	n = r.src.Int63()
+	r.lk.Unlock()
+	return
+}
+
+func (r *lockedSource) Seed(seed int64) {
+	r.lk.Lock()
+	r.src.Seed(seed)
+	r.lk.Unlock()
+}
+
+// SeededRand is a new RNG using a thread safe implementation of rand.Source
+var SeededRand = rand.New(&lockedSource{src: rand.NewSource(time.Now().UnixNano())})

vendor/github.com/aws/aws-sdk-go/internal/sdkrand/read.go

@@ -0,0 +1,12 @@
+//go:build go1.6
+// +build go1.6
+
+package sdkrand
+
+import "math/rand"
+
+// Read provides the stub for math.Rand.Read method support for go version's
+// 1.6 and greater.
+func Read(r *rand.Rand, p []byte) (int, error) {
+	return r.Read(p)
+}

vendor/github.com/aws/aws-sdk-go/internal/sdkrand/read_1_5.go

@@ -0,0 +1,25 @@
+//go:build !go1.6
+// +build !go1.6
+
+package sdkrand
+
+import "math/rand"
+
+// Read backfills Go 1.6's math.Rand.Reader for Go 1.5
+func Read(r *rand.Rand, p []byte) (n int, err error) {
+	// Copy of Go standard libraries math package's read function not added to
+	// standard library until Go 1.6.
+	var pos int8
+	var val int64
+	for n = 0; n < len(p); n++ {
+		if pos == 0 {
+			val = r.Int63()
+			pos = 7
+		}
+		p[n] = byte(val)
+		val >>= 8
+		pos--
+	}
+
+	return n, err
+}