Fix issues found by CI on Gitea runner

- cli.py: remove redundant cast to str (mypy strict, click 8.5+ types prompt);
  annotate prompt result explicitly
- test_storage.py: use now-relative timestamps instead of hardcoded 2026-08
  dates so history-filter tests do not rot over time
- add Gitea Actions CI workflow (.gitea/workflows/ci.yml)

src/selectel_ml_tui/cli.py

@@ -3,7 +3,6 @@
 from __future__ import annotations
 
 from pathlib import Path
-from typing import cast
 
 import click
 
@@ -49,10 +48,12 @@ def _prompt_str(
     default_note: str = "(Enter — оставить)",
 ) -> str:
     prompt = f"{label} [{current or 'пусто'}] {default_note}: "
-    value = click.prompt(prompt, default="", hide_input=hide_input, show_default=False)
+    value: str = click.prompt(
+        prompt, default="", hide_input=hide_input, show_default=False
+    )
     if value == "":
         return current
-    return cast(str, value)
+    return value
 
 
 @click.group()