Phase 5.2 -- Responsive Implementation

Parent: #762

Context

Responsive scope determined in #766 (Phase 0.2). This issue applies breakpoints and responsive behavior to all pages.

Scope (depending on #766 decision)

If desktop + tablet:

• Sidebar: collapsible to icon rail at tablet widths
• Cards: reflow from multi-column to fewer columns
• Charts: resize and simplify at smaller widths
• Tables: horizontal scroll or card-view alternative
• Command palette: full-width at small screens

If full mobile:

• All of the above plus:
• Bottom navigation bar (replaces sidebar)
• Touch-optimized interactions (larger tap targets, swipe gestures)
• Mobile-first chart alternatives

Deliverables

• All pages responsive per the scope from feat: define page structure and information architecture #766
• Breakpoint testing at all defined widths
• Sidebar collapse behavior
• Chart resize behavior
• No horizontal overflow at any breakpoint

Blocked by

• Phase 4 pages substantially complete
• feat: define page structure and information architecture #766 (responsive scope decision)