Providers factory (#250)

* Implement providers factory

* Multiple providers sync support

- Proper Multi-Provider Syncing: When you click sync on an account with multiple providers (e.g., both Plaid and SimpleFin), all provider items are synced
- Better API: The existing account.providers method already returns all providers, and account.provider returns the first one for backward compatibility
- Correct Holdings Deletion Logic: Holdings can only be deleted if ALL providers allow it, preventing accidental deletions that would be recreated on next sync
TODO: validate this is the way we want to go? We would need to check holdings belong to which account, and then check provider allows deletion. More complex
- Database Constraints: The existing validations ensure an account can have at most one provider of each type (one PlaidAccount, one SimplefinAccount, etc.)

* Add generic provider_import_adapter

* Finish unified import strategy

* Update app/models/plaid_account.rb

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
Signed-off-by: soky srm <sokysrm@gmail.com>

* Update app/models/provider/factory.rb

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
Signed-off-by: soky srm <sokysrm@gmail.com>

* Fix account linked by plaid_id instead of external_id

* Parse numerics to BigDecimal

Parse numerics to BigDecimal before computing amount; guard nils.

Avoid String * String and float drift; also normalize date.

* Fix incorrect usage of assert_raises.

* Fix linter

* Fix processor test.

* Update current_balance_manager.rb

* Test fixes

* Fix plaid linked account test

* Add support for holding per account_provider

* Fix proper account access

Also fix account deletion for simpefin too

* FIX match tests for consistency

* Some more factory updates

* Fix account schema for multipe providers

  Can do:
  - Account #1 → PlaidAccount + SimplefinAccount (multiple different providers)
  - Account #2 → PlaidAccount only
  - Account #3 → SimplefinAccount only

  Cannot do:
  - Account #1 → PlaidAccount + PlaidAccount (duplicate provider type)
  - PlaidAccount #123 → Account #1 + Account #2 (provider linked to multiple accounts)

* Fix account setup

- An account CAN have multiple providers (the schema shows account_providers with unique index on [account_id, provider_type])
  - Each provider should maintain its own separate entries
  - We should NOT update one provider's entry when another provider syncs

* Fix linter and guard migration

* FIX linter issues.

* Fixes

- Remove duplicated index
- Pass account_provider_id
- Guard holdings call to avoid NoMethodError

* Update schema and provider import fix

* Plaid doesn't allow holdings deletion

* Use ClimateControl for proper env setup

* No need for this in .git

---------

Signed-off-by: soky srm <sokysrm@gmail.com>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
Co-authored-by: Juan José Mata <juanjo.mata@gmail.com>

app/models/simplefin_entry/processor.rb

@@ -6,42 +6,26 @@ class SimplefinEntry::Processor
   end
 
   def process
-    SimplefinAccount.transaction do
-      entry = account.entries.find_or_initialize_by(plaid_id: external_id) do |e|
-        e.entryable = Transaction.new
-      end
-
-      entry.assign_attributes(
-        amount: amount,
-        currency: currency,
-        date: date
-      )
-
-      entry.enrich_attribute(
-        :name,
-        name,
-        source: "simplefin"
-      )
-
-      # SimpleFin provides no category data - categories will be set by AI or rules
-
-      if merchant
-        entry.transaction.enrich_attribute(
-          :merchant_id,
-          merchant.id,
-          source: "simplefin"
-        )
-      end
-
-      entry.save!
-    end
+    import_adapter.import_transaction(
+      external_id: external_id,
+      amount: amount,
+      currency: currency,
+      date: date,
+      name: name,
+      source: "simplefin",
+      merchant: merchant
+    )
   end
 
   private
     attr_reader :simplefin_transaction, :simplefin_account
 
+    def import_adapter
+      @import_adapter ||= Account::ProviderImportAdapter.new(account)
+    end
+
     def account
-      simplefin_account.account
+      simplefin_account.current_account
     end
 
     def data