feat: 角色视觉体系（头像按角色取）+ 时间注入（loop 每轮当前时间）

【角色视觉体系（红线：每个角色自己的头像/背景，绝不串用昔涟）】
- persona.go：Persona 加 Visual{avatar, chatBackground{landscape,portrait}} + DefaultAvatar；每个角色各自配。
- cyrene.yaml：昔涟配 avatar(3F-Q-Happy-1) + chatBackground(横/竖屏)。
- PersonaStore 加 Persona(id)；PersonaSummary 加 avatar/chatBackground；collectPersonas 按角色取
  Persona(id) 视觉（无视觉→空，前端回退默认占位，绝不串角色）。
- 前端：types PersonaRecord 加 avatar/chatBackground；persona.ts personaAvatar(p)=p?.avatar||默认占位
  (殊无昔涟 fallback)；store 加 currentPersona；App 挂载 fetchPersonas 取默认角色；
  TopBar/chat 头像改 personaAvatar(currentPersona)（写死昔涟头像已清除）。

【时间注入（她自然知道现在几点，深夜催睡交给人格/capacity）】
- options.go Options 加 Timezone；loop.go Loop 加 timeLocation/timeZoneName + New 解析 + loadTimezone；
  time.go currentTimeBlock()(当前时间+周几+时区，每轮刷新)；memory.go assembleContext 在「工作记忆」
  前注入时间 system(keyed 在 timeLocation!=nil，无时区不注入不破坏测试)；wire.go Timezone=a.cfg.Timezone。

go build/vet/test 全绿(gateway/loop/persona)；前端 tsc/vite build 75模块绿。红线无写死昔涟头像。

internal/persona/loader/persona.go

@@ -53,6 +53,26 @@ type AffectionParams struct {
 // Persona is a loaded persona definition. It describes who a character is (the
 // identity, personality, speech style, catchphrase, background, values) and
 // never restricts what that character can do.
+// PersonaVisual carries the persona-owned visual assets (per-role icon/avatar
+// and optional chat background). Each persona configures its OWN visuals; the UI
+// renders the current persona's resources, so one role never inherits another's.
+type PersonaVisual struct {
+	// Avatar is the persona's avatar image path (e.g. /images/Cyrene_Avatar/...).
+	Avatar string `yaml:"avatar,omitempty"`
+	// ChatBackground optionally sets the persona's chat backdrop, per orientation.
+	ChatBackground ChatBackground `yaml:"chatBackground,omitempty"`
+}
+
+// ChatBackground holds per-orientation chat wallpaper paths (landscape/portrait).
+type ChatBackground struct {
+	Landscape string `yaml:"landscape,omitempty"`
+	Portrait  string `yaml:"portrait,omitempty"`
+}
+
+// DefaultAvatar is the neutral fallback avatar shown when a persona has no
+// avatar configured (so a role never silently borrows another persona's view).
+const DefaultAvatar = "/images/User_Avatar/Default_Avatar.png"
+
 type Persona struct {
 	ID           string          `yaml:"id"`
 	Name         string          `yaml:"name"`
@@ -65,6 +85,7 @@ type Persona struct {
 	Values       []string        `yaml:"values"`
 	Emotion      EmotionParams   `yaml:"emotion"`
 	Affection    AffectionParams `yaml:"affection"`
+	Visual       PersonaVisual   `yaml:"visual,omitempty"`
 }
 
 // EmotionConfig converts this persona's own fields into the params consumed by