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/models/brain.py

@@ -0,0 +1,93 @@
+from sqlalchemy import Column, DateTime, Float, ForeignKey, Integer, String, Table, Text
+from sqlalchemy.dialects.sqlite import JSON
+
+from app.database import Base
+from app.models.base import BaseModel, utc_now
+
+
+brain_event_tags = Table(
+    "brain_event_tags",
+    Base.metadata,
+    Column("event_id", String(36), ForeignKey("brain_events.id"), primary_key=True),
+    Column("tag_id", String(36), ForeignKey("brain_tags.id"), primary_key=True),
+)
+
+brain_memory_tags = Table(
+    "brain_memory_tags",
+    Base.metadata,
+    Column("memory_id", String(36), ForeignKey("brain_memories.id"), primary_key=True),
+    Column("tag_id", String(36), ForeignKey("brain_tags.id"), primary_key=True),
+)
+
+brain_memory_sources = Table(
+    "brain_memory_sources",
+    Base.metadata,
+    Column("memory_id", String(36), ForeignKey("brain_memories.id"), primary_key=True),
+    Column("event_id", String(36), ForeignKey("brain_events.id"), primary_key=True),
+)
+
+
+class BrainEvent(BaseModel):
+    __tablename__ = "brain_events"
+
+    user_id = Column(String(36), ForeignKey("users.id"), nullable=False, index=True)
+    source_type = Column(String(50), nullable=False, index=True)
+    source_id = Column(String(36), nullable=False, index=True)
+    event_type = Column(String(50), nullable=False, index=True)
+    title = Column(String(255), nullable=True)
+    content_summary = Column(Text, nullable=True)
+    raw_excerpt = Column(Text, nullable=True)
+    metadata_ = Column(JSON, nullable=True)
+    importance_signal = Column(Float, default=0.0, nullable=False)
+    is_user_pinned = Column(Integer, default=0, nullable=False)
+    occurred_at = Column(DateTime, default=utc_now, nullable=False, index=True)
+    processed_at = Column(DateTime, nullable=True)
+    status = Column(String(20), default="pending", nullable=False, index=True)
+
+
+class BrainCandidate(BaseModel):
+    __tablename__ = "brain_candidates"
+
+    user_id = Column(String(36), ForeignKey("users.id"), nullable=False, index=True)
+    candidate_type = Column(String(50), nullable=False, index=True)
+    title = Column(String(255), nullable=False)
+    summary = Column(Text, nullable=False)
+    importance_score = Column(Float, default=0.0, nullable=False)
+    confidence_score = Column(Float, default=0.0, nullable=False)
+    time_scope = Column(String(20), default="short_term", nullable=False)
+    valid_from = Column(DateTime, nullable=True)
+    valid_to = Column(DateTime, nullable=True)
+    source_event_ids = Column(JSON, nullable=True)
+    reasoning_trace = Column(Text, nullable=True)
+    status = Column(String(20), default="new", nullable=False, index=True)
+    reviewed_at = Column(DateTime, nullable=True)
+
+
+class BrainMemory(BaseModel):
+    __tablename__ = "brain_memories"
+
+    user_id = Column(String(36), ForeignKey("users.id"), nullable=False, index=True)
+    memory_type = Column(String(50), nullable=False, index=True)
+    title = Column(String(255), nullable=False)
+    content = Column(Text, nullable=False)
+    importance = Column(Integer, default=5, nullable=False)
+    confidence = Column(Float, default=0.0, nullable=False)
+    timeline_date = Column(DateTime, nullable=True)
+    first_learned_at = Column(DateTime, default=utc_now, nullable=False)
+    last_reinforced_at = Column(DateTime, nullable=True)
+    reinforcement_count = Column(Integer, default=0, nullable=False)
+    status = Column(String(20), default="active", nullable=False, index=True)
+    origin_candidate_id = Column(String(36), ForeignKey("brain_candidates.id"), nullable=True)
+    origin_source_types = Column(JSON, nullable=True)
+    metadata_ = Column(JSON, nullable=True)
+
+
+class BrainTag(BaseModel):
+    __tablename__ = "brain_tags"
+
+    user_id = Column(String(36), ForeignKey("users.id"), nullable=False, index=True)
+    name = Column(String(100), nullable=False, index=True)
+    category = Column(String(50), nullable=False)
+    priority = Column(String(20), default="secondary", nullable=False, index=True)
+    score = Column(Float, default=0.0, nullable=False)
+    last_seen_at = Column(DateTime, nullable=True)