refactor(mcp): flatten to mcp_server package, drop src layout

Rename the import package surfsense_mcp -> mcp_server and remove the
src/ layer so the project mirrors the backend's shape (project folder
!= package name, e.g. surfsense_backend/app). Kills the redundant
surfsense_mcp/src/surfsense_mcp nesting.

Distribution name and console command (surfsense-mcp) are unchanged;
only python -m and internal import paths move to mcp_server. Dockerfile
CMD updated; no PYTHONPATH added since the editable install already
makes the package importable.

surfsense_mcp/mcp_server/features/knowledge_base/annotations.py

@@ -0,0 +1,34 @@
+"""Tool-call policy hints and shared parameter types for knowledge-base tools."""
+
+from __future__ import annotations
+
+from typing import Annotated
+
+from mcp.types import ToolAnnotations
+from pydantic import Field
+
+READ = ToolAnnotations(
+    readOnlyHint=True, destructiveHint=False, idempotentHint=True, openWorldHint=False
+)
+WRITE = ToolAnnotations(
+    readOnlyHint=False, destructiveHint=False, idempotentHint=False, openWorldHint=False
+)
+DELETE = ToolAnnotations(
+    readOnlyHint=False, destructiveHint=True, idempotentHint=False, openWorldHint=False
+)
+
+DocumentId = Annotated[
+    int,
+    Field(
+        description="Document id from surfsense_search_knowledge_base or "
+        "surfsense_list_documents results."
+    ),
+]
+
+DocumentTypes = Annotated[
+    list[str] | None,
+    Field(
+        description="Restrict to these document types, e.g. "
+        "['FILE', 'CRAWLED_URL', 'YOUTUBE_VIDEO']. Omit for all types."
+    ),
+]