feat: remote browser login persistence + balance display + UI consistency

- Retain login state in remote browser profiles (don't delete on disconnect)
- Add GET /api/browser-sessions/{id}/clipboard for clipboard sync
- Add POST /api/browser-sessions/{id}/autofill-login for manual credential fill
- Add DELETE /api/browser-sessions/profiles/{custom_page_id} for login clear
- Add balance tracking with configurable divisor (balance_divisor)
- Health check on session reuse, idle TTL eviction, background cleanup
- Add first-frame watchdog (10s timeout) to prevent infinite loading
- Reconnect browser on active=true when session was closed
- UI: uniform text-only inline buttons (websites + upstreams pages)
- Fix page switch race with closingRemoteSessionPromise

backend/app/schemas/upstream.py

@@ -29,6 +29,9 @@ class UpstreamCreate(BaseModel):
     enabled: bool = True
     check_interval_seconds: int = 600
     timeout_seconds: int = 30
+    balance_endpoint: str = ""
+    balance_response_path: str = ""
+    balance_divisor: float = 1.0
 
 
 class UpstreamUpdate(BaseModel):
@@ -42,6 +45,9 @@ class UpstreamUpdate(BaseModel):
     enabled: Optional[bool] = None
     check_interval_seconds: Optional[int] = None
     timeout_seconds: Optional[int] = None
+    balance_endpoint: Optional[str] = None
+    balance_response_path: Optional[str] = None
+    balance_divisor: Optional[float] = None
 
 
 class UpstreamResponse(BaseModel):
@@ -59,6 +65,11 @@ class UpstreamResponse(BaseModel):
     last_status: str
     last_checked_at: Optional[datetime]
     last_error: Optional[str]
+    balance: Optional[float] = None
+    balance_updated_at: Optional[datetime] = None
+    balance_endpoint: str = ""
+    balance_response_path: str = ""
+    balance_divisor: float = 1.0
     created_at: datetime
     updated_at: datetime