T03: plugin system framework + lifecycle + migrations + event bus + DI

- Plugin registry with discover/install/activate/deactivate/uninstall lifecycle
- PluginManifest Pydantic v2 schema (name, version, dependencies, routes, events, migrations)
- BasePlugin abstract class with lifecycle hooks (on_install/activate/deactivate/uninstall)
- Migration runner with tenant_id validator (rejects tables without tenant_id)
- Event bus integration: register/unregister listeners on activate/deactivate
- Service container DI: plugins receive db, cache, event_bus, storage, notifications
- Idempotent operations (activate active=200, deactivate inactive=200)
- UI registry for frontend component registration
- 47 new tests (14 ACs + 33 unit tests), 103 total tests pass
- Migration 0003: plugins + plugin_migrations tables
- Coverage: 85.92% for plugin modules

alembic/versions/0003_plugin_system.py

@@ -0,0 +1,55 @@
+"""T03: plugins + plugin_migrations tables.
+
+Revision ID: 0003_plugin_system
+Revises: 0002_contacts_fts
+Create Date: 2026-06-29
+"""
+
+from __future__ import annotations
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+revision: str = "0003_plugin_system"
+down_revision: Union[str, None] = "0002_contacts_fts"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # --- plugins table (system-wide, NOT tenant-scoped) ---
+    op.create_table(
+        "plugins",
+        sa.Column("id", postgresql.UUID(as_uuid=True), primary_key=True),
+        sa.Column("name", sa.String(80), nullable=False, unique=True),
+        sa.Column("display_name", sa.String(120), nullable=False),
+        sa.Column("version", sa.String(40), nullable=False),
+        sa.Column("status", sa.String(20), nullable=False, server_default="installed"),
+        sa.Column("installed", sa.Boolean, nullable=False, server_default=sa.text("true")),
+        sa.Column("active", sa.Boolean, nullable=False, server_default=sa.text("false")),
+        sa.Column("config", sa.Text, nullable=True),
+        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
+        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
+    )
+    op.create_index("ix_plugins_name", "plugins", ["name"], unique=True)
+
+    # --- plugin_migrations table (tracks which migrations have been applied) ---
+    op.create_table(
+        "plugin_migrations",
+        sa.Column("id", postgresql.UUID(as_uuid=True), primary_key=True),
+        sa.Column("plugin_name", sa.String(80), nullable=False),
+        sa.Column("migration_file", sa.String(255), nullable=False),
+        sa.Column("status", sa.String(20), nullable=False, server_default="applied"),
+        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
+        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
+        sa.UniqueConstraint("plugin_name", "migration_file", name="ix_plugin_migrations_unique"),
+    )
+    op.create_index("ix_plugin_migrations_plugin", "plugin_migrations", ["plugin_name"])
+
+
+def downgrade() -> None:
+    op.drop_table("plugin_migrations")
+    op.drop_table("plugins")