fix(git-gate): inline GIT_GATE_TIMEOUT_SECS to fix git-http ImportError

git_http_backend.py is copied flat into the sidecar bundle image as a
standalone script, not as part of the bot_bottle package, and
git_gate.py/git_gate_render.py are never copied in. Its relative
import of GIT_GATE_TIMEOUT_SECS crashed the git-http daemon (port
9420) on every startup, silently leaving the smart-HTTP git-gate
transport down while the other sidecar daemons stayed up.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

bot_bottle/git_http_backend.py

@@ -16,11 +16,16 @@ from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
 from pathlib import Path
 from urllib.parse import urlsplit
 
-from .git_gate import GIT_GATE_TIMEOUT_SECS
-
 
 DEFAULT_PORT = 9420
 
+# Mirrors git_gate_render.GIT_GATE_TIMEOUT_SECS. Duplicated rather than
+# imported: this module ships as a flat top-level sibling in the sidecar
+# bundle image (see Dockerfile.sidecars), not as part of the bot_bottle
+# package, so `bot_bottle.git_gate` and its dependency chain aren't
+# available at runtime.
+GIT_GATE_TIMEOUT_SECS = 15
+
 # Bound memory use while still allowing ordinary git push packfiles.
 MAX_BODY_BYTES = 100 * 1024 * 1024