feat(usage): add per-call token usage records table

Expose a paginated endpoint and UI table that lists individual LLM call
records (assistant messages with usage) per bot, showing time, session
type, model, provider, and token counts. Respects existing date / model
/ session-type filters and adds full-height loaders plus a max-width
layout to keep the usage page consistent with other top-level pages.

spec/swagger.yaml

@@ -2016,6 +2016,44 @@ definitions:
           type: string
         type: array
     type: object
+  handlers.TokenUsageRecord:
+    properties:
+      cache_read_tokens:
+        type: integer
+      cache_write_tokens:
+        type: integer
+      created_at:
+        type: string
+      id:
+        type: string
+      input_tokens:
+        type: integer
+      model_id:
+        type: string
+      model_name:
+        type: string
+      model_slug:
+        type: string
+      output_tokens:
+        type: integer
+      provider_name:
+        type: string
+      reasoning_tokens:
+        type: integer
+      session_id:
+        type: string
+      session_type:
+        type: string
+    type: object
+  handlers.TokenUsageRecordsResponse:
+    properties:
+      items:
+        items:
+          $ref: '#/definitions/handlers.TokenUsageRecord'
+        type: array
+      total:
+        type: integer
+    type: object
   handlers.TokenUsageResponse:
     properties:
       by_model:
@@ -6232,6 +6270,65 @@ paths:
       summary: Get token usage statistics
       tags:
       - token-usage
+  /bots/{bot_id}/token-usage/records:
+    get:
+      description: Paginated list of individual LLM call records (assistant messages
+        with usage) for a bot, with optional model and session type filters
+      parameters:
+      - description: Bot ID
+        in: path
+        name: bot_id
+        required: true
+        type: string
+      - description: Start date (YYYY-MM-DD)
+        in: query
+        name: from
+        required: true
+        type: string
+      - description: End date exclusive (YYYY-MM-DD)
+        in: query
+        name: to
+        required: true
+        type: string
+      - description: Optional model UUID to filter by
+        in: query
+        name: model_id
+        type: string
+      - description: 'Optional session type: chat, heartbeat, or schedule'
+        in: query
+        name: session_type
+        type: string
+      - description: Page size (default 20, max 100)
+        in: query
+        name: limit
+        type: integer
+      - default: 0
+        description: Offset
+        in: query
+        name: offset
+        type: integer
+      produces:
+      - application/json
+      responses:
+        "200":
+          description: OK
+          schema:
+            $ref: '#/definitions/handlers.TokenUsageRecordsResponse'
+        "400":
+          description: Bad Request
+          schema:
+            $ref: '#/definitions/handlers.ErrorResponse'
+        "403":
+          description: Forbidden
+          schema:
+            $ref: '#/definitions/handlers.ErrorResponse'
+        "500":
+          description: Internal Server Error
+          schema:
+            $ref: '#/definitions/handlers.ErrorResponse'
+      summary: List per-call token usage records
+      tags:
+      - token-usage
   /bots/{bot_id}/tools:
     post:
       description: MCP endpoint for tool discovery and invocation.