feat(07-01): DB migration 009, ORM updates, and LANGUAGE_INSTRUCTION in system prompts

- Migration 009: adds language col (VARCHAR 10, NOT NULL, default 'en') to portal_users
- Migration 009: adds translations col (JSONB, NOT NULL, default '{}') to agent_templates
- Migration 009: backfills es+pt translations for all 7 seed templates
- PortalUser ORM: language mapped column added
- AgentTemplate ORM: translations mapped column added
- system_prompt_builder.py: LANGUAGE_INSTRUCTION constant + appended before AI_TRANSPARENCY_CLAUSE
- system-prompt-builder.ts: LANGUAGE_INSTRUCTION constant + appended before AI transparency clause
- tests: TestLanguageInstruction class with 3 tests (all pass, 20 total)

packages/shared/shared/models/auth.py

@@ -61,6 +61,12 @@ class PortalUser(Base):
         default="customer_admin",
         comment="platform_admin | customer_admin | customer_operator",
     )
+    language: Mapped[str] = mapped_column(
+        String(10),
+        nullable=False,
+        server_default="en",
+        comment="UI and email language preference: en | es | pt",
+    )
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True),
         nullable=False,

packages/shared/shared/models/tenant.py

@@ -253,6 +253,12 @@ class AgentTemplate(Base):
         default=True,
         comment="Inactive templates are hidden from the gallery",
     )
+    translations: Mapped[dict[str, Any]] = mapped_column(
+        JSON,
+        nullable=False,
+        default=dict,
+        comment="JSONB map of locale -> {name, description, persona} translations. E.g. {'es': {...}, 'pt': {...}}",
+    )
     sort_order: Mapped[int] = mapped_column(
         Integer,
         nullable=False,

packages/shared/shared/prompts/system_prompt_builder.py

@@ -14,6 +14,14 @@ AI_TRANSPARENCY_CLAUSE = (
     "When directly asked if you are an AI, always disclose that you are an AI assistant."
 )
 
+# Language detection instruction (Phase 7 multilanguage feature).
+# Instructs agents to respond in the language the user writes in.
+# Supports English, Spanish, and Portuguese.
+LANGUAGE_INSTRUCTION = (
+    "Detect the language of each user message and respond in that same language. "
+    "You support English, Spanish, and Portuguese."
+)
+
 
 def build_system_prompt(
     name: str,
@@ -62,6 +70,9 @@ def build_system_prompt(
         )
         sections.append(f"Escalation rules:\n{rule_lines}")
 
+    # --- Language instruction (always present — Phase 7 multilanguage) ---
+    sections.append(LANGUAGE_INSTRUCTION)
+
     # --- AI transparency clause (always present, non-negotiable) ---
     sections.append(AI_TRANSPARENCY_CLAUSE)