New Design System + Codebase Refresh (#1823)

Since the very first 0.1.0-alpha.1 release, we've been moving quickly to add new features to the Maybe app. In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.

Now that "core" Maybe is complete, we're moving into a second phase of development where we'll be working hard to improve the accuracy of existing features and build additional features on top of "core". This PR is a quick overhaul of the existing codebase aimed to:

- Establish the brand new and simplified dashboard view (pictured above)
- Establish and move towards the conventions introduced in Cursor rules and project design overview #1788
- Consolidate layouts and improve the performance of layout queries
- Organize the core models of the Maybe domain (i.e. Account::Entry, Account::Transaction, etc.) and break out specific traits of each model into dedicated concerns for better readability
- Remove stale / dead code from codebase
- Remove overly complex code paths in favor of simpler ones

app/models/series.rb

@@ -0,0 +1,57 @@
+class Series
+  attr_reader :start_date, :end_date, :interval, :trend, :values
+
+  Value = Struct.new(
+    :date,
+    :date_formatted,
+    :trend,
+    keyword_init: true
+  )
+
+  class << self
+    def from_raw_values(values, interval: "1 day")
+      raise ArgumentError, "Must be an array of at least 2 values" unless values.size >= 2
+      raise ArgumentError, "Must have date and value properties" unless values.all? { |value| value.has_key?(:date) && value.has_key?(:value) }
+
+      ordered = values.sort_by { |value| value[:date] }
+      start_date = ordered.first[:date]
+      end_date = ordered.last[:date]
+
+      new(
+        start_date: start_date,
+        end_date: end_date,
+        interval: interval,
+        trend: Trend.new(
+          current: ordered.last[:value],
+          previous: ordered.first[:value]
+        ),
+        values: [ nil, *ordered ].each_cons(2).map do |prev_value, curr_value|
+          Value.new(
+            date: curr_value[:date],
+            date_formatted: I18n.l(curr_value[:date], format: :long),
+            trend: Trend.new(
+              current: curr_value[:value],
+              previous: prev_value&.[](:value)
+            )
+          )
+        end
+      )
+    end
+  end
+
+  def initialize(start_date:, end_date:, interval:, trend:, values:)
+    @start_date = start_date
+    @end_date = end_date
+    @interval = interval
+    @trend = trend
+    @values = values
+  end
+
+  def current
+    values.last.trend.current
+  end
+
+  def any?
+    values.any?
+  end
+end