feat(db): add sqlx migrate feature and renumber migration files

- Add 'migrate' feature to sqlx dependency
- Renumber migrations to fix duplicate version numbers (two 014 files)
- Re-sequence migrations 009-012 for continuous ordering
- Add ALTER TABLE ADD COLUMN IF NOT EXISTS baseline for notification
  table to handle existing databases missing newer columns
- Remove deleted IM migration files (009-012) that were superseded

migrate/012_release_assets_pr_enhancements.sql

@@ -0,0 +1,44 @@
+-- Release Assets - binary attachments for releases
+CREATE TABLE IF NOT EXISTS repo_release_asset (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    release_id UUID NOT NULL REFERENCES repo_release(id) ON DELETE CASCADE,
+    filename TEXT NOT NULL,
+    size_bytes BIGINT NOT NULL,
+    mime_type TEXT NOT NULL DEFAULT 'application/octet-stream',
+    storage_path TEXT NOT NULL,
+    url TEXT,
+    download_count BIGINT NOT NULL DEFAULT 0,
+    uploaded_by UUID REFERENCES "user"(id) ON DELETE SET NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+    deleted_at TIMESTAMPTZ
+);
+CREATE INDEX IF NOT EXISTS idx_repo_release_asset_release ON repo_release_asset(release_id, deleted_at);
+CREATE INDEX IF NOT EXISTS idx_repo_release_asset_deleted ON repo_release_asset(deleted_at) WHERE deleted_at IS NOT NULL;
+
+-- PR Templates (mirrors issue_template structure)
+CREATE TABLE IF NOT EXISTS pr_template (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    repo_id UUID NOT NULL REFERENCES repo(id) ON DELETE CASCADE,
+    name TEXT NOT NULL,
+    description TEXT,
+    title_template TEXT,
+    body_template TEXT NOT NULL DEFAULT '',
+    labels TEXT[] NOT NULL DEFAULT '{}',
+    active BOOLEAN NOT NULL DEFAULT true,
+    created_by UUID REFERENCES "user"(id) ON DELETE SET NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+CREATE INDEX IF NOT EXISTS idx_pr_template_repo ON pr_template(repo_id);
+
+-- PR Review Requests
+CREATE TABLE IF NOT EXISTS pr_review_request (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    pull_request_id UUID NOT NULL REFERENCES pull_request(id) ON DELETE CASCADE,
+    reviewer_id UUID NOT NULL REFERENCES "user"(id) ON DELETE CASCADE,
+    requested_by UUID NOT NULL REFERENCES "user"(id) ON DELETE CASCADE,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+CREATE INDEX IF NOT EXISTS idx_pr_review_request_pr ON pr_review_request(pull_request_id);
+CREATE UNIQUE INDEX IF NOT EXISTS idx_pr_review_request_pr_reviewer ON pr_review_request(pull_request_id, reviewer_id);