feat: fold bot-bottle-orchestrator into bot_bottle/orchestrator subpackage

Moves the orchestrator into bot_bottle/orchestrator/ so one install gets
everything. Entry point is now `python -m bot_bottle.orchestrator run`.

- Add bot_bottle/orchestrator/ with all 14 modules (verbatim move; internal
  imports were already relative, so no changes inside orchestrator modules)
- Rewrite bootstrap.py: remove the lazy bot_bottle import guard, use direct
  relative imports from ..contrib.*
- Add bot_bottle/contrib/forge/base.py: ScopedForge (read-anywhere / write-scoped)
- Add bot_bottle/contrib/gitea/client.py: GiteaClient + GiteaForge (urllib.request only)
- Add bot_bottle/contrib/gitea/forge_state.py: ForgeState + SqliteForgeStateStore
- Add tests/unit/orchestrator/ (82 tests: 63 migrated + 19 new for contrib modules)

Closes #321

tests/unit/orchestrator/test_config.py

@@ -0,0 +1,38 @@
+"""Unit: Config.from_env."""
+
+from __future__ import annotations
+
+import unittest
+from pathlib import Path
+
+from bot_bottle.orchestrator.config import Config
+
+
+class ConfigTest(unittest.TestCase):
+    def test_defaults(self):
+        c = Config.from_env({"HOME": "/home/x"})
+        self.assertEqual("bot-bottle", c.forge_org)
+        self.assertEqual(1800, c.watchdog_timeout_secs)
+        self.assertEqual("127.0.0.1", c.webhook_host)
+        self.assertEqual(8477, c.webhook_port)
+        self.assertEqual(Path("/home/x/.bot-bottle/forge-queue"), c.queue_dir)
+        self.assertIsNone(c.db_path)
+
+    def test_overrides(self):
+        c = Config.from_env({
+            "HOME": "/home/x",
+            "FORGE_ORG": "agents",
+            "FORGE_WATCHDOG_TIMEOUT": "60",
+            "FORGE_GITEA_API": "https://g.example/api/v1",
+            "FORGE_WEBHOOK_PORT": "9000",
+            "FORGE_DB_PATH": "/data/bb.db",
+        })
+        self.assertEqual("agents", c.forge_org)
+        self.assertEqual(60, c.watchdog_timeout_secs)
+        self.assertEqual("https://g.example/api/v1", c.gitea_api)
+        self.assertEqual(9000, c.webhook_port)
+        self.assertEqual(Path("/data/bb.db"), c.db_path)
+
+
+if __name__ == "__main__":
+    unittest.main()