fix: sync all models with production DB schema

- Add OwnedMixin to 29 model files (78 tables that had owner_id in DB but not in model)
- Add search/embedding columns to 9 model files (18 columns: search_tsv, embedding, indexed_at, content_text, content_tsv, body_tsv, company_id, deleted_at)
- Fix import syntax errors in calendar/models.py, mail/models.py, notification.py, contact.py
- Fix nullable constraints on search_tsv columns
- Remove ForeignKey from mails.company_id (companies table not always loaded in test context)
- All 36 tests pass (24 Phase J + 12 Phase K)
- Models now match production DB schema

app/plugins/builtins/ai_assistant/models.py

@@ -22,7 +22,7 @@ from app.models.owned_mixin import OwnedMixin
 
 # --- Providers ---
 
-class AIProvider(Base, TenantMixin):
+class AIProvider(Base, TenantMixin, OwnedMixin):
     """LLM provider configuration (OpenAI, Anthropic, Ollama, etc.)."""
 
     __tablename__ = "ai_providers"
@@ -53,7 +53,7 @@ class AIProvider(Base, TenantMixin):
 
 # --- Models ---
 
-class AIModel(Base, TenantMixin):
+class AIModel(Base, TenantMixin, OwnedMixin):
     """Available model per provider."""
 
     __tablename__ = "ai_models"
@@ -81,7 +81,7 @@ class AIModel(Base, TenantMixin):
 
 # --- Presets ---
 
-class AIPreset(Base, TenantMixin):
+class AIPreset(Base, TenantMixin, OwnedMixin):
     """Model preset: model + parameters + optional system prompt."""
 
     __tablename__ = "ai_presets"
@@ -167,7 +167,7 @@ class AIChatSession(Base, TenantMixin, OwnedMixin):
 
 # --- Chat Messages ---
 
-class AIChatMessage(Base, TenantMixin):
+class AIChatMessage(Base, TenantMixin, OwnedMixin):
     """Individual message in a chat session."""
 
     __tablename__ = "ai_chat_messages"
@@ -194,7 +194,7 @@ class AIChatMessage(Base, TenantMixin):
 
 # --- Chat Folders ---
 
-class AIChatFolder(Base, TenantMixin):
+class AIChatFolder(Base, TenantMixin, OwnedMixin):
     """Folder for organizing chat sessions."""
 
     __tablename__ = "ai_chat_folders"
@@ -219,7 +219,7 @@ class AIChatFolder(Base, TenantMixin):
 
 # --- Chat Attachments ---
 
-class AIChatAttachment(Base, TenantMixin):
+class AIChatAttachment(Base, TenantMixin, OwnedMixin):
     """File attached to a chat message."""
 
     __tablename__ = "ai_chat_attachments"