Harden SimpleFIN sync: protect user data, fix stuck syncs, optimize API calls (#671)

* Implement entry protection flags for sync overwrites

- Added `user_modified` and `import_locked` flags to `entries` table to prevent provider sync from overwriting user-edited and imported data.
- Introduced backfill migration to mark existing entries based on conditions.
- Enhanced sync and processing logic to respect protection flags, track skipped entries, and log detailed stats.
- Updated UI to display skipped/protected entries and reasons in sync summaries.

* Localize error details summary text and adjust `sync_account_later` method placement

* Restored schema.rb

---------

Co-authored-by: luckyPipewrench <luckypipewrench@proton.me>

db/migrate/20260115100000_add_entry_protection_flags.rb

@@ -0,0 +1,17 @@
+class AddEntryProtectionFlags < ActiveRecord::Migration[7.2]
+  def change
+    # user_modified: Set when user manually edits any field on an entry.
+    # Prevents provider sync from overwriting user's intentional changes.
+    # Does NOT prevent user from editing - only protects from automated overwrites.
+    add_column :entries, :user_modified, :boolean, default: false, null: false
+
+    # import_locked: Set when entry is created via CSV/manual import.
+    # Prevents provider sync from overwriting imported data.
+    # Does NOT prevent user from editing - only protects from automated overwrites.
+    add_column :entries, :import_locked, :boolean, default: false, null: false
+
+    # Partial indexes for efficient queries when filtering protected entries
+    add_index :entries, :user_modified, where: "user_modified = true", name: "index_entries_on_user_modified_true"
+    add_index :entries, :import_locked, where: "import_locked = true", name: "index_entries_on_import_locked_true"
+  end
+end

db/migrate/20260115100001_backfill_entry_protection_flags.rb

@@ -0,0 +1,34 @@
+class BackfillEntryProtectionFlags < ActiveRecord::Migration[7.2]
+  disable_ddl_transaction!
+
+  def up
+    # Backfill import_locked for entries that came from CSV/manual imports
+    # These entries have import_id set but typically no external_id or source
+    say_with_time "Marking CSV-imported entries as import_locked" do
+      execute <<-SQL.squish
+        UPDATE entries
+        SET import_locked = true
+        WHERE import_id IS NOT NULL
+          AND import_locked = false
+      SQL
+    end
+
+    # Backfill user_modified for entries where user has manually edited fields
+    # These entries have non-empty locked_attributes (set when user edits)
+    say_with_time "Marking user-edited entries as user_modified" do
+      execute <<-SQL.squish
+        UPDATE entries
+        SET user_modified = true
+        WHERE locked_attributes != '{}'::jsonb
+          AND locked_attributes IS NOT NULL
+          AND user_modified = false
+      SQL
+    end
+  end
+
+  def down
+    # Reversible but generally not needed
+    execute "UPDATE entries SET import_locked = false WHERE import_locked = true"
+    execute "UPDATE entries SET user_modified = false WHERE user_modified = true"
+  end
+end