feat: rename Docker Watcher to Tinyforge

Rebrand the project as Tinyforge to reflect its evolution from a Docker
container watcher into a self-hosted mini CI/deployment platform.

Rename covers: Go module path, Docker labels, DB/config filenames,
JWT issuer, Dockerfile binary, docker-compose, CI workflows, frontend
i18n, README with static sites docs, and all code comments.

internal/auth/local.go

@@ -41,7 +41,7 @@ type LocalAuth struct {
 // using HMAC-SHA256.
 func NewLocalAuth(encKey [32]byte) *LocalAuth {
 	mac := hmac.New(sha256.New, encKey[:])
-	mac.Write([]byte("docker-watcher-jwt-secret"))
+	mac.Write([]byte("tinyforge-jwt-secret"))
 	la := &LocalAuth{
 		jwtSecret: mac.Sum(nil),
 		blacklist: make(map[string]time.Time),
@@ -110,7 +110,7 @@ func (la *LocalAuth) GenerateToken(claims Claims) (SessionToken, error) {
 		RegisteredClaims: jwt.RegisteredClaims{
 			ExpiresAt: jwt.NewNumericDate(expiresAt),
 			IssuedAt:  jwt.NewNumericDate(time.Now()),
-			Issuer:    "docker-watcher",
+			Issuer:    "tinyforge",
 		},
 		UserID:   claims.UserID,
 		Username: claims.Username,