Add origin field and filter for ban sources (Tasks 1 & 2)

- Task 1: Mark imported blocklist IP addresses
  - Add BanOrigin type and _derive_origin() to ban.py model
  - Populate origin field in ban_service list_bans() and bans_by_country()
  - BanTable and MapPage companion table show origin badge column
  - Tests: origin derivation in test_ban_service.py and test_dashboard.py

- Task 2: Add origin filter to dashboard and world map
  - ban_service: _origin_sql_filter() helper; origin param on list_bans()
    and bans_by_country()
  - dashboard router: optional origin query param forwarded to service
  - Frontend: BanOriginFilter type + BAN_ORIGIN_FILTER_LABELS in ban.ts
  - fetchBans / fetchBansByCountry forward origin to API
  - useBans / useMapData accept and pass origin; page resets on change
  - BanTable accepts origin prop; DashboardPage adds segmented filter
  - MapPage adds origin Select next to time-range picker
  - Tests: origin filter assertions in test_ban_service and test_dashboard

backend/app/models/ban.py

@@ -48,6 +48,26 @@ class UnbanRequest(BaseModel):
     )
 
 
+#: Discriminator literal for the origin of a ban.
+BanOrigin = Literal["blocklist", "selfblock"]
+
+#: Jail name used by the blocklist import service.
+BLOCKLIST_JAIL: str = "blocklist-import"
+
+
+def _derive_origin(jail: str) -> BanOrigin:
+    """Derive the ban origin from the jail name.
+
+    Args:
+        jail: The jail that issued the ban.
+
+    Returns:
+        ``"blocklist"`` when the jail is the dedicated blocklist-import
+        jail, ``"selfblock"`` otherwise.
+    """
+    return "blocklist" if jail == BLOCKLIST_JAIL else "selfblock"
+
+
 class Ban(BaseModel):
     """Domain model representing a single active or historical ban record."""
 
@@ -65,6 +85,10 @@ class Ban(BaseModel):
         default=None,
         description="ISO 3166-1 alpha-2 country code resolved from the IP.",
     )
+    origin: BanOrigin = Field(
+        ...,
+        description="Whether this ban came from a blocklist import or fail2ban itself.",
+    )
 
 
 class BanResponse(BaseModel):
@@ -146,6 +170,10 @@ class DashboardBanItem(BaseModel):
         description="Organisation name associated with the IP.",
     )
     ban_count: int = Field(..., ge=1, description="How many times this IP was banned.")
+    origin: BanOrigin = Field(
+        ...,
+        description="Whether this ban came from a blocklist import or fail2ban itself.",
+    )
 
 
 class DashboardBanListResponse(BaseModel):