feat(sender): add outgoing Webmention pipeline

Scan generated h-entry documents for Webmention targets and track source
revisions and delivery state in the database.

Discover target endpoints, send Webmentions asynchronously, and reconcile
updated, removed, restored, and deleted sources across scans.

Add authenticated views for inspecting sent Webmentions and make the scanner
schedule configurable.

1 files changed, 66 insertions, 0 deletions

diff --git a/migrations/versions/681a2a9a1bc0_.py b/migrations/versions/681a2a9a1bc0_.py
new file mode 100644
index 0000000..2420b79
--- /dev/null
+++ b/migrations/versions/681a2a9a1bc0_.py
@@ -0,0 +1,66 @@
+"""empty message
+
+Revision ID: 681a2a9a1bc0
+Revises: f63641044cc1
+Create Date: 2026-08-14 13:40:55.149604
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '681a2a9a1bc0'
+down_revision = 'f63641044cc1'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_table('sources',
+    sa.Column('uuid', sa.Uuid(), nullable=False),
+    sa.Column('path', sa.Text(), nullable=False),
+    sa.Column('url', sa.Text(), nullable=False),
+    sa.Column('content_hash', sa.String(length=32), nullable=False),
+    sa.Column('revision', sa.Integer(), nullable=False),
+    sa.Column('last_seen_at', sa.DateTime(timezone=True), nullable=False),
+    sa.Column('revised_at', sa.DateTime(timezone=True), nullable=False),
+    sa.Column('deleted_at', sa.DateTime(timezone=True), nullable=True),
+    sa.PrimaryKeyConstraint('uuid'),
+    sa.UniqueConstraint('path'),
+    sa.UniqueConstraint('url')
+    )
+    op.create_table('sent_webmentions',
+    sa.Column('uuid', sa.Uuid(), nullable=False),
+    sa.Column('source_id', sa.Uuid(), nullable=False),
+    sa.Column('target', sa.Text(), nullable=False),
+    sa.Column('active', sa.Boolean(), nullable=False),
+    sa.Column('desired_revision', sa.Integer(), nullable=False),
+    sa.Column('processed_revision', sa.Integer(), nullable=True),
+    sa.Column('sent_revision', sa.Integer(), nullable=True),
+    sa.Column('status', sa.Enum('sent', 'unsupported', 'failed', name='sent_webmention_status', native_enum=False), nullable=True),
+    sa.Column('failure_reason', sa.Text(), nullable=True),
+    sa.Column('endpoint', sa.Text(), nullable=True),
+    sa.Column('response_status', sa.Integer(), nullable=True),
+    sa.Column('status_url', sa.Text(), nullable=True),
+    sa.Column('last_attempted_at', sa.DateTime(timezone=True), nullable=True),
+    sa.Column('last_sent_at', sa.DateTime(timezone=True), nullable=True),
+    sa.ForeignKeyConstraint(['source_id'], ['sources.uuid'], ondelete='CASCADE'),
+    sa.PrimaryKeyConstraint('uuid'),
+    sa.UniqueConstraint('source_id', 'target', name='uq_sent_webmention_source_target')
+    )
+    with op.batch_alter_table('sent_webmentions', schema=None) as batch_op:
+        batch_op.create_index(batch_op.f('ix_sent_webmentions_source_id'), ['source_id'], unique=False)
+
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table('sent_webmentions', schema=None) as batch_op:
+        batch_op.drop_index(batch_op.f('ix_sent_webmentions_source_id'))
+
+    op.drop_table('sent_webmentions')
+    op.drop_table('sources')
+    # ### end Alembic commands ###