[Feature request tracker] Add multi-account evidence and the account workflow

Parent: #57014 Delivery step: 3 ## Parent user story > As an account owner, I can record each account's evidence for a shared request, so product teams can understand who asked and why. ## Outcome of this step The manual tracker supports multiple affected accounts and preserves evidence for each account. Users can work from either the request or account context. ## Starting state #81884 provides a searchable manual request lifecycle with one account link. ## Scope - Link multiple accounts to one request. - Store account-specific quote, summary, source type, source URL, and requested date as approved in #81882. - Support more than one evidence item for an account when required by the contract. - Group evidence by account in request detail. - Add a Requests section to the expanded Customer Analytics account view. - Link an existing request and add evidence from the account context. - Remove one account link without changing other accounts or the shared request. - Record link and evidence changes in activity history. ## Out of scope - Vitally import. - GitHub status synchronization. - Weighted scoring or MRR ranking. - Automated duplicate detection. ## Additive design Extend the account link created in #81883. Preserve the shared request record and manual lifecycle from #81884. ## Acceptance criteria - [ ] One request can link to multiple accounts. - [ ] Evidence remains attached to the correct account. - [ ] The account view lists only requests linked to that account. - [ ] Linking from the account view does not duplicate the shared request. - [ ] Removing one account leaves other links and evidence unchanged. ## Test setup Use an editor, a viewer, accounts named `Acme` and `Globex`, and one request from #81884. ## UI testing 1. Open the request and link Acme with one quote and source URL. 2. Link Globex with different evidence. 3. Refresh and confirm that each item appears under the correct account. 4. Open Acme and inspect its Requests section. 5. Link another existing request and add evidence from Acme. 6. Return to the shared request detail. 7. Remove only Globex. Expected result: - Both surfaces show the same shared records. - Account-specific evidence never moves between accounts. - Removing Globex does not change Acme or the shared fields. - The viewer can inspect permitted evidence but cannot change it. ## Automated tests Cover relation constraints, team isolation, multiple evidence rows, account filtering, create/remove behavior, activity history, and both interface entry points. ## Dependencies - Blocked by: #81884 - Blocks: #81888 and #81890 ## Rollout and production verification Run the earlier create and lifecycle journeys. Then verify the two-account journey from both request and account routes.