Add brain memory services and APIs

Introduce the backend pieces for brain memory ingestion, routing, and
system telemetry so the new knowledge workflows can project data into a
brain view. The supporting tests lock in the new behavior and keep the
expanded backend surface stable.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/schemas/brain.py

@@ -0,0 +1,57 @@
+from datetime import datetime
+
+from pydantic import BaseModel
+
+
+class BrainOverviewOut(BaseModel):
+    active_memory_count: int
+    important_tag_count: int
+    secondary_tag_count: int
+    recent_memory_titles: list[str]
+
+
+class BrainMemoryOut(BaseModel):
+    id: str
+    memory_type: str
+    title: str
+    content: str
+    importance: int
+    confidence: float
+    status: str
+    created_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class BrainTagOut(BaseModel):
+    id: str
+    name: str
+    category: str
+    priority: str
+    score: float
+
+    model_config = {"from_attributes": True}
+
+
+class BrainEventOut(BaseModel):
+    id: str
+    source_type: str
+    source_id: str
+    event_type: str
+    title: str | None
+    content_summary: str | None
+    status: str
+    created_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class BrainTagGroupsOut(BaseModel):
+    important: list[BrainTagOut]
+    secondary: list[BrainTagOut]
+
+
+class BrainLearnRunOut(BaseModel):
+    events_considered: int
+    candidates_created: int
+    memories_promoted: int