Pass context.exclude_newer to libmambapy Database

Convert the exclude_newer duration/timestamp from conda's config
into a Unix timestamp cutoff and pass it to libmambapy's Database
constructor as exclude_newer_timestamp. This enables native
--exclude-newer filtering in the libmamba solver backend.

Depends on:
- conda/conda#15761 (exclude_newer config + parse_duration_to_seconds)
- mamba-org/mamba#4228 (exclude_newer_timestamp in Database::Settings)

Author: jezdez

conda_libmamba_solver/index.py

@@ -347,10 +347,25 @@ def _init_db(self) -> Database:
             home_dir=str(Path.home()),
             current_working_dir=os.getcwd(),
         )
-        db = Database(params)
+        db = Database(
+            params,
+            exclude_newer_timestamp=self._exclude_newer_timestamp(),
+        )
         db.set_logger(logger_callback)
         return db
 
+    @staticmethod
+    def _exclude_newer_timestamp():
+        """Convert context.exclude_newer to a Unix timestamp for libmambapy."""
+        value = context.exclude_newer
+        if not value:
+            return None
+        import time
+
+        from conda.cli.helpers import parse_duration_to_seconds
+
+        return int(time.time() - parse_duration_to_seconds(value))
+
     def _load_channels(
         self,
         urls_to_channel: dict[str, Channel] | None = None,

news/exclude-newer

@@ -0,0 +1,21 @@
+### Enhancements
+
+* Pass `context.exclude_newer` to libmambapy's `Database` as
+  `exclude_newer_timestamp`, enabling native `--exclude-newer` support
+  when the upstream mamba PR lands. (#15759)
+
+### Bug fixes
+
+* <news item>
+
+### Deprecations
+
+* <news item>
+
+### Docs
+
+* <news item>
+
+### Other
+
+* <news item>