Add v0.1.3 backend features: metadata fields and search

Backend Changes:
- Add estimated_minutes field to tasks (stored as integer minutes)
- Add tags field (JSON array) for categorizing tasks
- Add flag_color field for visual priority indicators
- Add search endpoint (/api/search) with project filtering
- Update JSON import to handle new metadata fields

Frontend Changes:
- Display version v0.1.3 in header
- Add search API client function
- Add format utility for time display (30m, 1.5h, etc.)

Example Data:
- Update example-import.json with time estimates, tags, and flags
- Demonstrate nested metadata inheritance

Note: Frontend UI for displaying/editing these fields in progress

backend/app/models.py

@@ -1,4 +1,4 @@
-from sqlalchemy import Column, Integer, String, Text, DateTime, ForeignKey, Enum
+from sqlalchemy import Column, Integer, String, Text, DateTime, ForeignKey, Enum, JSON
 from sqlalchemy.orm import relationship
 from datetime import datetime
 import enum
@@ -34,6 +34,9 @@ class Task(Base):
     description = Column(Text, nullable=True)
     status = Column(Enum(TaskStatus), default=TaskStatus.BACKLOG, nullable=False)
     sort_order = Column(Integer, default=0)
+    estimated_minutes = Column(Integer, nullable=True)
+    tags = Column(JSON, nullable=True)
+    flag_color = Column(String(50), nullable=True)
     created_at = Column(DateTime, default=datetime.utcnow)
     updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)