chore(frontend): remove the deprecated project feature

[aglinxinyuan]

What changes were proposed in this PR?

Removes the deprecated project feature from the Angular frontend. The feature was hidden behind projects_enabled = false in #3343 (2025-04-02) and has been unmaintained since; #5172 reached consensus to delete it rather than keep carrying it.

This is the frontend half. The backend endpoints and the database schema go separately, so this PR is safe to land on its own — the /project endpoints simply stop being called.

27 files deleted, 55 edited (+79 / −4798).

Area	What went
Components	the whole user-project/ tree — list page, section page, list item, public-project modal, add/remove-workflow modals (22 files)
Services	UserProjectService, StubUserProjectService, PublicProjectService
Types	DashboardProject / PublicProject, SearchResult.project, isDashboardProject, DashboardWorkflow.projectIDs
Routing	user/project, user/project/:pid, the USER_PROJECT constant, 6 app.module.ts declarations
Config	SidebarTabs.projects_enabled, the sidebar tab, the admin-settings toggle
Search / filters	project filter chips, projectIds search params, the project arm of the entry builder, EntityType.Project

UI impact. Every surface below projects_enabled was already hidden by default, so a default deployment renders identically before and after — no user-visible change to screenshot. The one exception is the admin settings page, which loses its now-meaningless Projects toggle row (twelve switches → eleven).

Before:  Admin Settings ▸ tabs ▸ [Your Work][Projects][Workflows][Datasets]…
After:   Admin Settings ▸ tabs ▸ [Your Work][Workflows][Datasets]…

Two adjacent cleanups were deliberately left out of scope, since they are unrelated dead code rather than part of this feature: hub-search-result.component.ts's @Input() accessLevel and search-results.component.ts's @Input() pid.

Any related issues, documentation, discussions?

Closes #7460

Removal agreed in #5172; the backend and schema half is #7461. Also updates frontend/README.md, the only doc line that named the feature.

How was this PR tested?

Existing tests, adjusted where a project fixture was doing double duty as a generic sample (e.g. the "non-shareable entry" case now uses "file" instead of "project"), and deleted where a test existed solely to exercise project behaviour.

cd frontend && npx tsc --noEmit && npx ng test --watch=false && yarn format:ci

Check	Result
tsc --noEmit	clean
ng test --watch=false	195 files, 4118 passed, 1 skipped, 0 failed
eslint ./src	clean
prettier-eslint --list-different	clean

ng build was also run: it reports 13 errors, all inside node_modules (monaco .ttf/.svg/.css loaders) and none under src/app. Confirmed pre-existing rather than caused by this change by building a pristine origin/main worktree against the same node_modules — identical 13 errors.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.31%. Comparing base (e03d971) to head (6da735a).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7463      +/-   ##
============================================
- Coverage     85.32%   85.31%   -0.02%     
  Complexity     4151     4151              
============================================
  Files          1169     1156      -13     
  Lines         46740    46108     -632     
  Branches       5202     5146      -56     
============================================
- Hits          39882    39337     -545     
+ Misses         5148     5068      -80     
+ Partials       1710     1703       -7     

Flag	Coverage Δ		*Carryforward flag
access-control-service	70.00% <ø> (ø)		Carriedforward from e03d971
agent-service	85.50% <ø> (ø)		Carriedforward from e03d971
amber	80.88% <ø> (ø)		Carriedforward from e03d971
computing-unit-managing-service	50.72% <ø> (ø)		Carriedforward from e03d971
config-service	65.97% <ø> (ø)		Carriedforward from e03d971
file-service	69.05% <ø> (ø)		Carriedforward from e03d971
frontend	87.91% <100.00%> (+0.05%)	⬆️
notebook-migration-service	78.89% <ø> (ø)		Carriedforward from e03d971
pyamber	97.51% <ø> (ø)		Carriedforward from e03d971
workflow-compiling-service	26.31% <ø> (ø)		Carriedforward from e03d971

*This pull request uses carry forward flags. Click here to find out more.

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