M3 wiki-links: [[links]] + backlinks

- Migration 0009: note_links (source_id, target_norm). Parse [[...]] from body on
  create/update and rewrite the source's links. GET /api/notes/titles (owner
  {id,title} index for client-side resolution); GET /api/notes/<id>/backlinks.
- Frontend: titles store; LinkedText renders [[Title]] styled on cards; editor
  shows Links (outgoing, resolve/create-on-click) + Linked-from (backlinks),
  clicking navigates the editor to the target note (board + search).
- notes store: fetchOne, createTitled. DB-free link-parser tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

alembic/versions/0009_note_links.py

@@ -0,0 +1,31 @@
+"""note_links (wiki-links)
+
+Revision ID: 0009
+Revises: 0008
+Create Date: 2026-07-20
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import UUID
+
+revision = "0009"
+down_revision = "0008"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "note_links",
+        sa.Column("id", UUID(as_uuid=True), primary_key=True),
+        sa.Column("source_id", UUID(as_uuid=True), sa.ForeignKey("notes.id", ondelete="CASCADE"), nullable=False),
+        sa.Column("target_norm", sa.Text(), nullable=False),
+    )
+    op.create_index("ix_note_links_source", "note_links", ["source_id"])
+    op.create_index("ix_note_links_target", "note_links", ["target_norm"])
+
+
+def downgrade() -> None:
+    op.drop_index("ix_note_links_target", table_name="note_links")
+    op.drop_index("ix_note_links_source", table_name="note_links")
+    op.drop_table("note_links")