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

bot_bottle/orchestrator/targeting.py

@@ -0,0 +1,51 @@
+"""Decide whether an assigned issue is agent-targeted, and for whom.
+
+An issue is forge-targeted when BOTH hold:
+- it carries a `bot-bottle:<agent>` label naming the agent, and
+- at least one assignee is a member of the configured org.
+
+An optional `bot-bottle-bottle:<name>` label overrides bottle selection.
+The forge is duck-typed: any object with `is_org_member(org, user)`.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Protocol
+
+from .config import BOTTLE_LABEL_PREFIX, LABEL_PREFIX
+from .model import IssueAssigned
+
+
+class Membership(Protocol):
+    def is_org_member(self, org: str, username: str) -> bool: ...
+
+
+@dataclass(frozen=True)
+class Target:
+    agent_name: str
+    bottle_override: str | None
+
+
+def parse_labels(labels: tuple[str, ...]) -> tuple[str | None, str | None]:
+    """Return (agent_name, bottle_override) parsed from labels."""
+    agent: str | None = None
+    bottle: str | None = None
+    for label in labels:
+        if label.startswith(BOTTLE_LABEL_PREFIX):
+            bottle = label[len(BOTTLE_LABEL_PREFIX):] or None
+        elif label.startswith(LABEL_PREFIX):
+            agent = label[len(LABEL_PREFIX):] or None
+    return agent, bottle
+
+
+def resolve_target(
+    event: IssueAssigned, forge: Membership, org: str
+) -> Target | None:
+    """Return the `Target` for a forge-targeted issue, or None to ignore."""
+    agent, bottle = parse_labels(event.labels)
+    if not agent:
+        return None
+    if not any(forge.is_org_member(org, a) for a in event.assignees):
+        return None
+    return Target(agent_name=agent, bottle_override=bottle)