Add persistence, multi-repo watch list, and background polling0.3.0

Closes #1-#5 (milestones 0.2.0, 0.3.0).

- Flat JSON persistence (PersistedState/PersistenceStore) in Application
  Support, chosen over SwiftData since the dataset is small and the
  existing model types are plain Codable value types passed across actor
  boundaries.
- Repo watch list, per-event seen-state, and last-fetch timestamps are
  now persisted instead of living only in memory.
- Configurable minimum severity filter, applied from a cached raw fetch
  so changing it doesn't require a network round-trip.
- Multi-repo support: SecurityEventStore now loops over a persisted watch
  list instead of one hardcoded repo, with an in-popover UI (gear button)
  to add/remove repos.
- Background polling every 15 minutes, layered on top of the existing
  refresh-on-open and manual refresh, so the feed stays fresh even while
  the popover is closed.

1 files changed, 26 insertions, 0 deletions

diff --git a/octosentry/PersistedState.swift b/octosentry/PersistedState.swift
new file mode 100644
index 0000000..3ef4234
--- /dev/null
+++ b/octosentry/PersistedState.swift
@@ -0,0 +1,26 @@
+//
+//  PersistedState.swift
+//  octosentry
+//
+//  Everything the app remembers across launches: the repo watch list,
+//  local-only seen-state per event, last-fetch timestamp per repo, and the
+//  minimum severity filter. Flat JSON over SwiftData (see #1) — small,
+//  inspectable, and these are already plain Codable values passed across
+//  actor boundaries, not reference types tied to a persistence context.
+//
+
+import Foundation
+
+nonisolated struct PersistedState: Codable {
+    var watchedRepos: [String]
+    var seenEventIDs: Set<String>
+    var lastFetchByRepo: [String: Date]
+    var minimumSeverity: SecurityEventSeverity
+
+    static let placeholder = PersistedState(
+        watchedRepos: ["ccleberg/cleberg.net"],
+        seenEventIDs: [],
+        lastFetchByRepo: [:],
+        minimumSeverity: .low
+    )
+}