Filings UI: there should be a separate error dialog if Keycloak token is expired/invalid

### Title: Keycloak Expired or Invalid

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Currently there is a single error dialog if the dashboard cannot be loaded because of any failure (can't get JWT/ roles/ business info/ entity info/ tasks/ filings/ etc) (see App.vue). The purpose of this ticket is to improve feedback to the user by giving them a separate message (dialog) when their Keycloak token is expired or invalid (since that is a very different failure from a GET (API) error).

See also #2378 and #2494. These tickets are not duplicates but highly related.

**This ticket should be implemented AFTER the "new" Keycloak validation is implemented in coops-ui so that that functionality can be used here. (Otherwise, we can only check if the token has expired, not if it's valid.)**

## Description:
* As a user
* I want a specific notification when my business dashboard is unavailable because my Keycloak token is expired or invalid
* so that I know my problem is authentication not authorization.

**Acceptance Criteria**
* GIVEN ... (you or your condition)
* WHEN ... (what you do)
* THEN ... (what you see)

**Dependencies? (If so, link dependency in the ticket, make it visible in a team´s backlog)**

**Validation Rules? (If yes, list here)**

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**DoR for User Story:**
- [ ] Do we have a prioritized Sprint Backlog?
- [ ] Defects, user stories and other work the team has committed to are contained in the sprint backlog?
- [ ] Any hidden work?
- [ ] All team members availability (days) & capacity (in SP) is known for the Sprint?
- [ ] All users stories meet the DoR?

**Definition of Ready:**
1. [ ] Does User Story have full flow of business rules, happy and alternate paths, etc.?
2. [ ] Requirements & expected behavior included in the User Story?
3. [ ] Are the dependencies known/ understood?
4. [ ] Dev team accepts user experience artifacts
5. [ ] If there are validation rules, are they defined (UI, Data, Role-Action)?
6. [ ] Does this User Story needs stakeholder approval?
7. [ ] Is this user story small enough to be completed in a Sprint?
8. [ ] What do we possible have to do re Change Management? - a) GCPE, …?

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**Definition of Done:**
1) [ ] Check Requirements against completed tasks
2) [ ] Completed stories verified in Dev and Test
3) [ ] Confirm Test cases built and succeeding
4) [ ] No regression test failures
5) [ ] Test coverage acceptable by Product Owner???
6) [ ] Ticket merged to master or story branch
7) [ ] Developer to list Config changes/ Update documents and designs
8) [ ] Design / Solution accepted by Product Owner
9) [ ] UX Approved
10) [ ] Can be demoed in Sprint Review
11) [ ] Release ticket is created and this US is linked to it

Start by reading App.vue and the new Keycloak validation in coops-ui, which this issue identifies as a prerequisite. Trace how dashboard-load failures reach the existing error dialog. Done means expired or invalid tokens produce a separate user message from GET/API failures, with the behavior covered by the project's relevant tests.

Written by the indexing model from the issue text.