feat(workspace): full server + sync implementation, all tests green

- solitaire_server: Axum auth, sync push/pull, leaderboard, daily
  challenge, account deletion, JWT middleware, rate limiting via
  tower_governor, SQLite migrations, health endpoint
- solitaire_server: expose build_test_router (no rate limiting) so
  integration tests work without a peer IP in oneshot requests
- solitaire_sync: SyncPayload, merge logic, shared API types
- solitaire_data: SyncProvider trait, LocalOnlyProvider,
  SolitaireServerClient, auth_tokens keyring integration, blanket
  Box<dyn SyncProvider> impl
- solitaire_data/settings: derive Default on SyncBackend (clippy fix)
- .sqlx/: offline query cache so server compiles without a live DB
- sqlx: removed non-existent "offline" feature flag
- keyring v2: fixed Entry::new() returning Result<Entry>
- sqlx 0.8: all SQLite TEXT columns wrapped in Option<T>
- Integration tests: max_connections(1) on in-memory pool so all
  connections share the same schema

All 191 tests pass; cargo clippy -D warnings clean.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.sqlx/query-04d8dced0cc309bc0d968ab8f542a7f6c504ce7c2f682c0bef35dfe441ffb6e8.json

@@ -0,0 +1,20 @@
+{
+  "db_name": "SQLite",
+  "query": "SELECT goal_json FROM daily_challenges WHERE date = ?",
+  "describe": {
+    "columns": [
+      {
+        "name": "goal_json",
+        "ordinal": 0,
+        "type_info": "Text"
+      }
+    ],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": [
+      false
+    ]
+  },
+  "hash": "04d8dced0cc309bc0d968ab8f542a7f6c504ce7c2f682c0bef35dfe441ffb6e8"
+}

.sqlx/query-2e61cd30a6cd3e0937dd096b4f94493e8bcb8c10687d0f8c0592fe38ed956fa6.json

@@ -0,0 +1,20 @@
+{
+  "db_name": "SQLite",
+  "query": "SELECT id FROM users WHERE username = ?",
+  "describe": {
+    "columns": [
+      {
+        "name": "id",
+        "ordinal": 0,
+        "type_info": "Text"
+      }
+    ],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": [
+      true
+    ]
+  },
+  "hash": "2e61cd30a6cd3e0937dd096b4f94493e8bcb8c10687d0f8c0592fe38ed956fa6"
+}

.sqlx/query-2f12541a6b99acf6d9e8f7ad13438df4ab92edcbfa01f38930aae63f1554b534.json

@@ -0,0 +1,26 @@
+{
+  "db_name": "SQLite",
+  "query": "SELECT id, password_hash FROM users WHERE username = ?",
+  "describe": {
+    "columns": [
+      {
+        "name": "id",
+        "ordinal": 0,
+        "type_info": "Text"
+      },
+      {
+        "name": "password_hash",
+        "ordinal": 1,
+        "type_info": "Text"
+      }
+    ],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": [
+      true,
+      false
+    ]
+  },
+  "hash": "2f12541a6b99acf6d9e8f7ad13438df4ab92edcbfa01f38930aae63f1554b534"
+}

.sqlx/query-57c93a6acd7eea44d00412e62f0d3fed7ffbe4cd759353d29f38a8eb37f69112.json

@@ -0,0 +1,38 @@
+{
+  "db_name": "SQLite",
+  "query": "SELECT l.display_name, l.best_score, l.best_time_secs, l.recorded_at\n           FROM leaderboard l\n           JOIN users u ON u.id = l.user_id\n           WHERE u.leaderboard_opt_in = 1\n           ORDER BY\n               CASE WHEN l.best_score IS NULL THEN 1 ELSE 0 END ASC,\n               l.best_score DESC,\n               CASE WHEN l.best_time_secs IS NULL THEN 1 ELSE 0 END ASC,\n               l.best_time_secs ASC",
+  "describe": {
+    "columns": [
+      {
+        "name": "display_name",
+        "ordinal": 0,
+        "type_info": "Text"
+      },
+      {
+        "name": "best_score",
+        "ordinal": 1,
+        "type_info": "Integer"
+      },
+      {
+        "name": "best_time_secs",
+        "ordinal": 2,
+        "type_info": "Integer"
+      },
+      {
+        "name": "recorded_at",
+        "ordinal": 3,
+        "type_info": "Text"
+      }
+    ],
+    "parameters": {
+      "Right": 0
+    },
+    "nullable": [
+      false,
+      true,
+      true,
+      false
+    ]
+  },
+  "hash": "57c93a6acd7eea44d00412e62f0d3fed7ffbe4cd759353d29f38a8eb37f69112"
+}

.sqlx/query-5e9e61cae887a08e4224fbea43a047c093bf5a4413499bfec858e302efa91bc3.json

@@ -0,0 +1,12 @@
+{
+  "db_name": "SQLite",
+  "query": "UPDATE users SET leaderboard_opt_in = 1 WHERE id = ?",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": []
+  },
+  "hash": "5e9e61cae887a08e4224fbea43a047c093bf5a4413499bfec858e302efa91bc3"
+}

.sqlx/query-720edc3b85eec90744179f2c73ed9798814b734a2f3d57405ef95772ae66a24d.json

@@ -0,0 +1,12 @@
+{
+  "db_name": "SQLite",
+  "query": "INSERT INTO sync_state (user_id, stats_json, achievements_json, progress_json, last_modified)\n           VALUES (?, ?, ?, ?, ?)\n           ON CONFLICT(user_id) DO UPDATE SET\n               stats_json        = excluded.stats_json,\n               achievements_json = excluded.achievements_json,\n               progress_json     = excluded.progress_json,\n               last_modified     = excluded.last_modified",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Right": 5
+    },
+    "nullable": []
+  },
+  "hash": "720edc3b85eec90744179f2c73ed9798814b734a2f3d57405ef95772ae66a24d"
+}

.sqlx/query-73ffdf5be39aa5c4c160c2f77d6634a6970eeb4e1d3395f045ded747f0ce9d2a.json

@@ -0,0 +1,12 @@
+{
+  "db_name": "SQLite",
+  "query": "DELETE FROM users WHERE id = ?",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": []
+  },
+  "hash": "73ffdf5be39aa5c4c160c2f77d6634a6970eeb4e1d3395f045ded747f0ce9d2a"
+}

.sqlx/query-8697100790ebcdf4058812cf6debad8f9a13ac91c2d0ef20cff3bd4bb9385360.json

@@ -0,0 +1,12 @@
+{
+  "db_name": "SQLite",
+  "query": "INSERT INTO leaderboard (user_id, display_name, recorded_at)\n           VALUES (?, ?, ?)\n           ON CONFLICT(user_id) DO UPDATE SET\n               display_name = excluded.display_name,\n               recorded_at  = excluded.recorded_at",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Right": 3
+    },
+    "nullable": []
+  },
+  "hash": "8697100790ebcdf4058812cf6debad8f9a13ac91c2d0ef20cff3bd4bb9385360"
+}

.sqlx/query-a908d8d19647494f2ac2f801dc9c977f7ce23b44779da1567049856eab922645.json

@@ -0,0 +1,32 @@
+{
+  "db_name": "SQLite",
+  "query": "SELECT stats_json, achievements_json, progress_json FROM sync_state WHERE user_id = ?",
+  "describe": {
+    "columns": [
+      {
+        "name": "stats_json",
+        "ordinal": 0,
+        "type_info": "Text"
+      },
+      {
+        "name": "achievements_json",
+        "ordinal": 1,
+        "type_info": "Text"
+      },
+      {
+        "name": "progress_json",
+        "ordinal": 2,
+        "type_info": "Text"
+      }
+    ],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": [
+      false,
+      false,
+      false
+    ]
+  },
+  "hash": "a908d8d19647494f2ac2f801dc9c977f7ce23b44779da1567049856eab922645"
+}

.sqlx/query-ab537795ba39fdd28c502a8b9e615f53e7cb08f3eddd8f0574f4dc8156436de5.json

@@ -0,0 +1,12 @@
+{
+  "db_name": "SQLite",
+  "query": "INSERT OR IGNORE INTO daily_challenges (date, seed, goal_json) VALUES (?, ?, ?)",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Right": 3
+    },
+    "nullable": []
+  },
+  "hash": "ab537795ba39fdd28c502a8b9e615f53e7cb08f3eddd8f0574f4dc8156436de5"
+}

.sqlx/query-cc1e091bf5e46e6d98baf94bac6d9ac1ca1845eff7c4b8196dd2efb93fd9e0dd.json

@@ -0,0 +1,12 @@
+{
+  "db_name": "SQLite",
+  "query": "INSERT INTO users (id, username, password_hash, created_at) VALUES (?, ?, ?, ?)",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Right": 4
+    },
+    "nullable": []
+  },
+  "hash": "cc1e091bf5e46e6d98baf94bac6d9ac1ca1845eff7c4b8196dd2efb93fd9e0dd"
+}