feat(schemas): T35 add Pydantic public API schemas

- PublicStatsResponse: summary + period info
- PublicUsageResponse: paginated usage items
- PublicKeyInfo: key metadata with stats (no values!)
- ApiToken schemas: create, response, create-response
- 25 unit tests, 100% coverage

src/openrouter_monitor/schemas/__init__.py

@@ -20,6 +20,19 @@ from openrouter_monitor.schemas.stats import (
     UsageStatsCreate,
     UsageStatsResponse,
 )
+from openrouter_monitor.schemas.public_api import (
+    ApiTokenCreate,
+    ApiTokenCreateResponse,
+    ApiTokenResponse,
+    PaginationInfo,
+    PeriodInfo,
+    PublicKeyInfo,
+    PublicKeyListResponse,
+    PublicStatsResponse,
+    PublicUsageItem,
+    PublicUsageResponse,
+    SummaryInfo,
+)
 
 __all__ = [
     "UserRegister",
@@ -37,4 +50,16 @@ __all__ = [
     "StatsByModel",
     "StatsByDate",
     "DashboardResponse",
+    # Public API schemas
+    "ApiTokenCreate",
+    "ApiTokenCreateResponse",
+    "ApiTokenResponse",
+    "PublicStatsResponse",
+    "PublicUsageResponse",
+    "PublicKeyInfo",
+    "PublicKeyListResponse",
+    "SummaryInfo",
+    "PeriodInfo",
+    "PublicUsageItem",
+    "PaginationInfo",
 ]