## Summary
Adds an **Analysis** button to the transactions toolbar (left of
Categorize) that opens a bottom-sheet dashboard summarizing the
transactions matching the current filters. Built around the Miami-trip
use case: tag a trip, filter to it, and see where the money went.
Everything is behind the existing `TransactionAnalysis` feature flag
(button hidden + endpoint returns 403 when off).
## Behavior
- **Button**: hidden unless `features.transactionAnalysis`. Disabled
until at least one filter is applied — desktop shows a hover tooltip,
mobile a tap dialog, both reading *"Apply a filter to enable this
button."*
- **Drawer** (vaul bottom-sheet, like the importer): fetches
`/api/transactions/analysis` with the current filters on open. Skeleton
+ empty/error states.
- **Charts**: KPI cards · spending over time (income/expense bars +
cumulative line, auto daily/monthly bucketing) · category donut + ranked
list (only when >1 category) · per-tag bars (only when >1 label).
- **Manual day override**: the *Avg / day* card has an editor to
override the date span used for the daily average (tickets bought months
ahead skew the span). Resolution precedence: matching saved filter's
`analysis_days` → `localStorage[fingerprint]` → auto span. Edits persist
to localStorage always, and sync to the saved filter when the current
filters match one.
## Backend
- `Api/TransactionAnalysisController@summary` — reuses
`Transaction::applyFilters()` + `IndexTransactionRequest`, converts to
the user's base currency via `ExchangeRateService` (rates preloaded),
rolls categories up through `CategoryTree`.
- `GET /api/transactions/analysis`.
- `analysis_days` (nullable) on `saved_filters` + `PATCH
/api/saved-filters/{id}/analysis-days`.
## Tests
- Pest: analysis endpoint (flag gating, totals, category/tag breakdown,
day/month bucketing, cumulative) + saved-filter day override
(set/clear/forbidden/invalid).
- Vitest: button gating (hidden/disabled/opens) + day-override
resolution (auto / saved-precedence / localStorage fallback / persists
to saved filter).
- New `lang/es.json` keys for all added strings.
## Notes
- Data is always sourced from the backend.
- The flag is still off by default — enable `TransactionAnalysis`
per-user to try it.
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