feat: seed script, forgot-password, hover cards, shortcuts, OpenAPI docs, runbook (phase 12)

- scripts/seed.go: idempotent demo data per §11.11 (make seed)
- forgot/reset password: SMTP-gated, one-shot TTL tokens, uniform responses
  against enumeration, sessions revoked on reset; login page link + pages
- profile hover cards on [data-user-card] elements (§11.13)
- keyboard shortcuts: g b/m/t/h navigation, / focuses search (§10)
- bulk archive endpoint (§11.9)
- hand-written OpenAPI 3.1 covering §6, served at /api/docs + yaml download
- make backup / make restore (mongodump archive via the mongo container)
- README: quick start, demo data, runbook, breaker/job operations, working
  Caddy + nginx reverse-proxy samples (WS block, client_max_body_size),
  documented later-stubs (§11.24)
- smoke.sh now exercises register → logout → login → me → board → pages

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

internal/store/indexes.go

@@ -51,10 +51,6 @@ func EnsureIndexes(ctx context.Context, db *mongo.Database) error {
 			{Keys: bson.D{{Key: "participantIds", Value: 1}, {Key: "lastMessageAt", Value: -1}}},
 			{Keys: bson.D{{Key: "kind", Value: 1}, {Key: "customerId", Value: 1}}},
 		},
-		"messages": {
-			// ULID _id is time-ordered, so this serves history pagination.
-			{Keys: bson.D{{Key: "conversationId", Value: 1}, {Key: "_id", Value: 1}}},
-		},
 		"notifications": {
 			{Keys: bson.D{{Key: "userId", Value: 1}, {Key: "readAt", Value: 1}, {Key: "createdAt", Value: -1}}},
 		},
@@ -62,6 +58,14 @@ func EnsureIndexes(ctx context.Context, db *mongo.Database) error {
 			{Keys: bson.D{{Key: "expiresAt", Value: 1}}, Options: options.Index().SetExpireAfterSeconds(0)},
 			{Keys: bson.D{{Key: "userId", Value: 1}}},
 		},
+		"passwordResets": {
+			{Keys: bson.D{{Key: "expiresAt", Value: 1}}, Options: options.Index().SetExpireAfterSeconds(0)},
+		},
+		"messages": {
+			// ULID _id is time-ordered, so this serves history pagination.
+			{Keys: bson.D{{Key: "conversationId", Value: 1}, {Key: "_id", Value: 1}}},
+			{Keys: bson.D{{Key: "attachments.fileId", Value: 1}}, Options: options.Index().SetSparse(true)},
+		},
 		"auditLog": {
 			{Keys: bson.D{{Key: "at", Value: -1}}},
 			{Keys: bson.D{{Key: "entityId", Value: 1}, {Key: "at", Value: -1}}},